TORONTO -- Second baseman Neil Walker was absent from the Pirates' lineup on Thursday as he continues to nurse a sore lower back. Xavier Paul was also out with tightness in his right hamstring, which flared up on him just before the start of Wednesday's game.

Walker characterized his back as "certainly not bad," but he has been dealing with some alignment issues for almost a week now. It was at its worst, he said, last Friday against the Red Sox, and improved over the weekend. But it then began plaguing him again after two games on the Rogers Centre's artificial turf.

"We're hoping it's just a little bit of misalignment and that we've gotten my pelvis straightened out," said Walker, who has just two hits in 17 at-bats since the ailment first surfaced. "You have to be sure to take care of yourself, especially when you're on this kind of stuff out there. I think it's a culmination of maybe not maintaining it correctly."

Taking Walker's place at second on Thursday was Josh Harrison, who had extensive experience at the position in the Minors.

Paul said he was feeling better a day after his hamstring tightened up, but manager Clint Hurdle said he'd be hesitant to use Paul in the series finale against the Blue Jays. Hurdle also suggested that a move to the disabled list could be necessary for Paul if he is not able to play by Saturday.

"He might get some more treatment," Hurdle said. "He went out and ran limited. We'll try to make a better, accurate read on it [Friday]."

Morton to return to the mound on Friday

TORONTO -- Following 10 days of rest, plenty of long toss and a focus on specifics with his delivery and extension, Charlie Morton will return to the mound on Friday against the Nationals. It will be Morton's first start since a June 20 outing that was followed by the Pirates' decision to have him take an extended respite to get back in sync.

Morton denied ever feeling fatigue, but on Thursday he did note benefits of stepping back and working through some kinks.

"There's nothing glaring," said Morton, who posted a 2.52 ERA through his first 11 starts and then a 12.27 mark in his most recent three. "If anything, my mechanics have gotten better since the beginning of the year. It's just my arm. The stuff coming out of my hand wasn't as live as it had been."

In order to try to get the life back, Morton worked through a formulaic long-toss program with pitching coach Ray Searage. The purpose of those sessions, during which Morton would throw four-seam fastballs, was to reacquaint Morton with getting full extension in his motion. There was also an emphasis put on making sure that, during his delivery, he held his tuck a little longer than he had recently.

The lack of extension is what the Pirates believe led to the lack of life and limited sink on Morton's pitches for much of June.

"There's no doubt about it," Searage said. "I look at the velocity. I look at the life on the ball. The last couple of games and the last couple of 'pens, we were just trying to get him through and hoping for the best."

Despite the extended layoff, Morton will not be on any sort of pitch count on Friday, manager Clint Hurdle said.

"I've been wanting to pitch ever since I pitched last," said an anxious Morton. "It's been frustrating."

Diaz impressing following subpar April

TORONTO -- Signed in the offseason to be particularly potent against left-handed pitching, Matt Diaz won over few fans during his first month with the Pirates. He hit just .208 and had nearly as many strikeouts (nine) as he did total hits (10).

His batting average may still be recovering from a terrible April, but the production has been there lately for the corner outfielder. Placed in the cleanup spot for the third time this season on Thursday, Diaz entered the final game of a three-game series against the Blue Jays having batted .302 in his last 27 games.

He added two more hits -- one an RBI single -- in the Pirates' 6-2 win over the Blue Jays

"You want to contribute," Diaz said. "June was one of my favorite months of baseball that I've ever had. I was able to contribute to this team that has been grinding it out all year. It's fun."

Since the start of May, he has hit .289. No one on the Pirates' roster has a batting average that high for the season.

"It's been a much more productive month of at-bats," manager Clint Hurdle said. "Historically speaking, yeah, this is the time that there is some movement. We could use some movement. He's doing everything he can to have better at-bats and be more productive as well. He's well aware of the challenges he had early and the disappointment that came with it for him personally."

Surprisingly, it was the left-handed pitchers who gave Diaz so much trouble early on. Since beginning the year 2-for-23 against southpaws, Diaz has 18 hits in his last 51 at-bats against lefties. That includes going 8-for-17 in the past two weeks.

Much to his delight, the Pirates will draw two left-handed starters in their upcoming four-game weekend series against the Nationals.

Bucs bits

• Rehabbing third baseman Pedro Alvarez played four innings for Class A Advanced Bradenton on Wednesday. He finished 0-for-2 with a walk.

• Top pitching prospect Jameson Taillon allowed one hit in three scoreless innings for Class A West Virginia on Wednesday. He struck out four and did not walk a batter.

• Nick Leyva was unable to coach third base on Thursday night due to back pain. First base coach Luis Silverio shifted to the third-base coaching box, while extra coach Mark Strittmatter took over the duties on the first-base side. It marked the second time this year that Strittmatter has coached first.

• Both catcher Dusty Brown and lefty Aaron Thompson cleared waivers and were outrighted to the Minors. Brown joins the Triple-A club in Indianapolis and Thompson returns to Double-A Altoona, where he was 3-6 with a 4.97 ERA in 16 games (12 starts) before being designated for assignment.

• Indianapolis first baseman Matt Hague has been named to the International League All-Star team. The Triple-A game is scheduled to be played on July 13. Hague has hit .324 with eight homers and 43 RBIs in 79 games this season.

• Triple-A catcher Jason Jaramillo is tentatively scheduled to begin his rehab assignment next week. Jaramillo, who has been nursing a sore arm, is likely to be added to the Pirates' roster once that rehab assignment is complete.