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6/11/2014 12:04 A.M. ET

Walker undergoes appendectomy, placed on DL

PITTSBURGH -- Somewhat lost in the news surrounding the Pirates calling up top prospect Gregory Polanco was the fact they'll also be without their second-best hitter for at least a few weeks.

Second baseman Neil Walker underwent a successful appendectomy Monday night and was placed on the 15-day disabled list after he was a late scratch to the lineup. Walker is hitting .280 this season with 11 homers, the most among National League second basemen, and 35 RBIs.

Manager Clint Hurdle said he did not know the specifics on how long Walker would be sidelined, but acknowledged the lineup would take a hit without him.

"We've encouraged him to stay mentally strong, to do what he's able to do when he's able to do it," Hurdle said. "This could very well -- based on his makeup, his focus -- turn out to be a blessing in disguise."

This is Walker's third DL stint in the last 13 months. He was sidelined twice last season, once in May with a laceration on his right index finger and again two months later with a strained right oblique. He also sat out nearly three weeks near the end of the 2012 season with tightness in his lower back.

Polanco filled Walker's spot on the 25-man roster and also will take over his place in the order, as the right fielder is slated to hit second Tuesday against the Cubs. On the field, Hurdle said Josh Harrison will fill the second base void most of the time while Walker recovers, but utility man Clint Barmes is starting there Tuesday.

Polanco reflects on first Major League game

PITTSBURGH -- It was not the way he wanted the day to end. That's the first thing Gregory Polanco said. Yet, it was still a triumphant day for him.

"I know we lost," Polanco said after the Pirates had dropped his Major League debut, 7-3, to the Chicago Cubs. "Still, I'm excited to play my first game. It was very good."

Polanco went 1-for-5, collecting his first big league hit in the third inning, ahead of an Andrew McCutchen home run.

"It felt very good. Now I have that one, and can just play the game," he said.

Before he had a hit to his name, Polanco had a standing ovation. The early in-house portion of a crowd that would swell to 31,567 with walk-up patrons arose to welcome Polanco as soon as he left the on-deck circle in the bottom of the first.

"That made me a little nervous," he said of the reception, grinning broadly.

It was an eventful evening for the Bucs. How eventful it will become in hindsight has yet to be determined and Clint Hurdle, for one, wished for people to be mindful of that.

"I'm not going to get in front of it, I just want to see him play," said the Pirates manager, his way of discouraging jumping to any quick impressions. "He's going to be fine with every game, with every at-bat, with every inning in the field.

"You got to see that swing. To barrel that one ball up into left field, left-on-left. To get that swing off -- that was nice to see."

Liriano placed on DL with left oblique strain

PITTSBURGH -- Francisco Liriano was pulled from a start in the fourth inning Tuesday with what manager Clint Hurdle called a "left oblique strain." Liriano landed on the disabled list and is the second Pirates' starter to do so this week.

Right-hander Stolmy Pimentel has been recalled from his rehab assignment and reinstated from the 15-day disabled list.

After his 55th pitch of the night, Liriano walked to the back of the mound, indicating something was wrong. A trainer took a look and talked with the lefty, who threw a few warmup pitches after the consult, but decided he could no longer pitch.

After the game, Hurdle gave a strong indication Liriano will miss at least his next start.

"I'm not a doctor. A left oblique strain, it might be a medical record if a guy can come back in four days and pitch," Hurdle said. "We have that on our side if we want to break a record. With what's going on, we'll make a better decision [Wednesday]."

Liriano had an MRI on Wednesday which confirmed the injury. Liriano noted he must have tweaked something just on one pitch and said he was still feeling some soreness when he spoke with reporters after the game, nearly three hours since he pitched. He added it's the first time he's had an ailment like this in his career and initially thought it was just a cramp.

A veteran lefty, Liriano is 1-6 with a 4.60 ERA in 14 starts the season. He surrendered a two-run homer to Anthony Rizzo in the first inning of Tuesday's game and allowed three hits and four strikeouts before exiting.

Liriano joins right-hander Gerrit Cole (6-3, 3.64 ERA), who was placed there Sunday with right shoulder fatigue.

In his debut, Polanco bats second in lineup

PITTSBURGH -- As if there was a need to further call attention to Gregory Polanco's unique talents and unlimited potential, Pirates manager Clint Hurdle inadvertently provided it when he posted his lineup for Tuesday night's game against the Cubs.

Pedro Alvarez, the reigning co-home run king of the National League, was not in it because a left-hander, Travis Wood, was pitching for Chicago.

However, not only was Polanco, who also hits from the left side, in the lineup, he was in the key No. 2 spot in the order -- behind Josh Harrison and ahead of Andrew McCutchen. The rookie ended up going 1-for-5 with a single in his second MLB at-bat in the 7-3 loss to the Cubs.

"Alvarez has had a tough going against this pitcher," Hurdle said of his third baseman, 1-for-18 with seven strikeouts against Wood. "Having Polanco in the two-hole just looked right.

"His mindset at the plate ... he has always demonstrated the stubborn approach to stay inside the ball and focus on [hitting it to] left-center field, so he might be more comfortable than other people with the angle from a left-hander," Hurdle said. "From all the reports I've gotten, there is not a lot of give in his swing against a left-handed pitcher."

Polanco thus inherited the normal lineup home of Neil Walker, whose placement on the DL following an appendectomy created a roster spot and need for him. Walker is tied for the team lead both with 11 homers and 35 RBIs.

"With Walker's absence," Hurdle said, "we're looking for some offense to supplement what's been taken away. You got a guy [Polanco] who hits the ball, has discipline at the plate, runs, and has been an on-base percentage guy throughout his career."

Pirates welcome Polanco to the Major Leagues

PITTSBURGH -- Gerrit Cole opened the doors of the Pirates' clubhouse to a larger-than-usual media contingent and facetiously asked, "Is Polanco here or something?"

Yes, the lengthy wait for 22-year-old Gregory Polanco's debut came to an end Tuesday when the outfielder went 1-for-5 with a single in his second MLB at-bat. Out went speculation and in came the frenzy of his debut, which was impossible to ignore in Pittsburgh, much less the Bucs' clubhouse.

Polanco arrived at PNC Park for the first time in his life earlier Tuesday morning after being told of his promotion Monday night. Polanco will try to keep his emotions in check when he takes the field for the first time, but just like any player making his debut, Josh Harrison said he noticed an in-awe thrill of the big leagues in Polanco.

"He did what most people do," said Harrison, whose locker neighbors Polanco's. "I walked in, he was sitting face-forward in his locker. We come up behind him, tap him, he turns around and smiles. We give him a handshake and a hug. You can tell he's excited to be here, but he's ready to play."

Asked of what advice his new teammates gave him, Polanco said: "Don't try to do anything different, just try to do the same thing you do. I know you're going to be excited, it's your first day. Try to stay in stay in control."

In control is exactly what the right fielder was this entire season for Triple-A Indianapolis, posting a .347 average, seven homers, 49 RBIs and a .945 OPS in 62 games. Pirates players were well aware of what Polanco was doing and knew his callup was imminent.

And now that the time is here, Andrew McCutchen -- a first-round pick who had a well-publicized debut in 2009 -- was having flashbacks of his first Major League game.

"My first year when I was up, it hit me sometime during the game that I was actually in the big leagues," McCutchen said. "I would be in the outfield, getting ready for a pitch and I would just be like 'I'm living my dream right now. This is crazy.' I still have instances. Polanco being here, you fall back to that."

Manager Clint Hurdle said he knows "this clubhouse will embrace, and if need be, protect" Polanco. Though there were cameras following him from a press conference through batting practice, his teammates, who he had played with before in Spring Training, gave him at least some sense of normalcy, as Polanco shared a few laughs with Harrison and fellow outfielders Starling Marte and McCutchen.

"I know he's probably getting a little frustrated with media and all the buzz, 'When's he coming up?' and this and that," Harrison said. "Now that it's finally here, he'll be fine."

First number, last word

56: Stolen bases by Starling Marte since the start of the 2013 season, tied for second most in the National League. Eric Young leads with 63 steals.

"We'll continue to remind him that he's not carrying a country. He's not carrying an organization. Let's be real about what we're doing. We're playing a game." -- Clint Hurdle, on lightening whatever pressure debuting rookie Gregory Polanco might be feeling via the virtue of perspective.

Worth noting

• The next step in Gerrit Cole's rehab program depends on how he feels after Monday's flat-ground throwing session. Immediately afterward, Cole said the exercise "felt good."

• In their 34th home game of the season, the Bucs faced a left-handed pitcher for only the second time. Travis Wood's only predecessor was the Reds' Tony Cingrani, on April 24.

• Per club policy, the Pirates do not reveal a precise number of walk-up tickets sold to any game, but based on the projected and actual attendance for Tuesday night's game, Polanco's debut generated more than 6,000 walk-ups. Expected attendance on Military Appreciation Night was 26,000, and an early visual pegged the crowd at about 32,000.

Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. Stephen Pianovich is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.