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3/19/2014 10:42 P.M. ET

Bucs' Stewart has surgery on right knee

FORT MYERS, Fla. -- Pirates backup catcher Chris Stewart had arthroscopic right knee surgery Wednesday and is expected to miss four to six weeks. Dr. James Andrews performed the surgery after confirming the team doctors' initial diagnosis.

The exact length of Stewart's absence will depend on how the knee reacts to the surgery in the coming days, though the expected timetable would put him on track to return in mid to late April.

With Stewart out for the start of the regular season, it remained unclear who would handle the backup catching duties. Prospect Tony Sanchez currently sits behind starter Russell Martin on the depth chart, but the Pirates have expressed their desire to have Sanchez playing in an everyday role at Triple-A as opposed to once a week in the Majors behind Martin. Sanchez is rated No. 14 on MLB.com's list of the Pirates' top prospects.

The only other in-house options beyond Sanchez are Nevin Ashley and Omir Santos, both of whom received invitations to Major League camp after signing Minor League contracts. The lack of depth options could lead the Pirates to pursue a veteran backup through the trade market, allowing Sanchez to begin the year with Triple-A Indianapolis.

Hurdle uses first challenge vs. Red Sox

FORT MYERS, Fla. -- Pirates manager Clint Hurdle on Wednesday night used the new replay system for the first time, challenging an inning-ending out at second base against the Red Sox.

With one out and a runner on second in the top of the seventh, Pirates outfielder Jaff Decker roped a comebacker to Red Sox pitcher Burke Badenhop. Badenhop spun and fired behind the runner at second base, catching pinch-runner Michael Martinez in a rundown between second and third base.

Red Sox third baseman Will Middlebrooks tagged out Martinez, then sprinted toward second base and dived to tag out Decker, who was trying to advance to second during the rundown. Second-base umpire Fieldin Culbreth ruled Decker out on the play and, after a brief review, the call was upheld.

Seeking defense, Lambo loses offensive pop

FORT MYERS, Fla. -- Pirates first baseman Andrew Lambo entered Spring Training knowing he had a very real opportunity to land a platoon gig alongside Gaby Sanchez at first base.

Not much has gone right for Lambo in his quest to earn that job, though the 25-year-old did end an 0-for-18 skid with a base hit in the sixth inning of Wednesday's 4-2 victory against the Red Sox.

"If you've been familiar with the situation and gone through [a position battle] before, I'm sure it's a little easier," Lambo said, "but being my first year of actually doing it, sure you think about it at times -- but not all that much. I'm trying to get myself ready for a pro season, whether it be in Pittsburgh, Indy, Altoona, Bradenton, doesn't matter."

Originally an outfielder, Lambo showed an offensive pop -- he hit 32 home runs and slugged .574 last season between Double-A Altoona and Triple-A Indianapolis -- that led the Pirates to give him some reps at first base to see if he could perform well enough defensively to form a platoon with Sanchez. But the offensive game has not been there this spring for Lambo, who is hitting .088 (3-for-34) with no extra-base hits after going 1-for-3 with a walk, stolen base and a run scored on Wednesday.

"It's been tough so far, but I'll keep doing my work, and everything will come around," Lambo said before Wednesday's game. "And at the same time, I'm not preparing only to try to make this ball club. I'm getting ready and preparing myself to hopefully play a full, productive season somewhere, wherever it is."

For the time being, Lambo remains in camp alongside fellow left-handed hitting first basemen Chris McGuiness and Travis Ishikawa, who are both competing for the same platoon opportunity. Ishikawa went 2-for-3 on Wednesday with his second homer of the spring.

"You keep going, day by day, and hopefully things will work out," Lambo said. "We've got a great group of guys in here, and it's going to come down to one guy, and that's it. There's nothing else to say. You just go out there and do the best you can, and hopefully it's you."

Worth noting

• Pirates utility man Chase d'Arnaud left Wednesday's game in the bottom of the eighth inning with a right eye contusion. Walking off under his own power, d'Arnaud sustained the injury while pursuing a Daniel Nava liner into the left-center field gap. Playing center field, d'Arnaud raced into the gap but came up just shy on a diving attempt, allowing the ball to then skip under his glove and glance off the right side of his face.

Paul Casella is a reporter for MLB.com. Follow him on Twitter @paul_casella. This story was not subject to the approval of Major League Baseball or its clubs.