ST. LOUIS -- The upbeat attitude John Danks has been exhibiting during the latter days of his stint on the disabled list took a bit of a hit Thursday when he felt slightly abnormal soreness in his left shoulder.

"It's kind of discouraging, but it's kind of expected," the White Sox right-hander said. "Hopefully I feel well enough to throw a side tomorrow."

Danks was placed on the disabled list retroactive to May 20 with a left shoulder strain. He had worked far enough back in the process to where he hurled four innings and 61 pitches during a rehab start for Triple-A Charlotte Tuesday in Columbus. When he felt fine after playing catch on Wednesday, a return to the rotation against the Cubs at home at the start of next week truly seemed possible.

This latest bout of soreness could be a setback. Danks and the White Sox won't know until he throws that scheduled bullpen session before Friday's series opener in Los Angeles.

"I'd imagine if I can't throw a side, then who knows," Danks said. "I don't know what their plan is anyway at this point. I'm worrying about throwing a side now."

"Everybody has that soreness, but he's the one who knows whether it's that good one or it's the same thing creeping back up again," said White Sox manager Robin Ventura. "He won't pitch if it's one of those where he feels like he did before."

Much of this soreness was expected after Danks amped up his rehab a bit when facing hitters in a game situation for the first time since his last start May 19 at Wrigley Field. Danks compared the feeling to Spring Training, where a pitcher gets that first wave of soreness and works through it.

There was a little soreness for Danks after his first side session during this rehab. Friday's throwing session will let Danks know if he also can work through this round.

"Obviously I didn't expect to feel quite this sore," Danks said. "I've never had this before, so I really didn't know what to expect. I was just hoping I would bounce back a little better than I have. It's part of it. You kind of go without throwing, and it's going to be sore."

Peavy a big fan of Cubs' Dempster

ST. LOUIS -- Ryan Dempster has started to make his way through the trade rumor mill, even with six weeks before the July 31 non-waiver Trade Deadline, after Cubs president Theo Epstein had a conversation with the veteran hurler prior to Wednesday's game at Wrigley.

If a current American League contender such as the Tigers and/or White Sox pursue and eventually add Dempster, who has full no-trade veto power as a 10-year veteran having played at least five years for the Cubs, it would be the right-hander's first foray into the AL.

That change is not an easy one to make even for National League Cy Young winners, as Jake Peavy found out firsthand when moving from the Padres to the White Sox in 2009.

"There's no doubt this is a better league," Peavy said. "It's a different league, it's a deeper league. It's a tougher league to pitch in. I'll stand by those comments 100 percent. There's more money over here.

"It seems like the free agents end up over here. We took the two best players out of the NL last year and we got them over here this year. You don't get to face the same bottom of the order over here, so it's not what it is in the NL. That's not taking anything away from the NL. But as far as a pitcher, you have to work a little bit harder in this league. It's a well-known fact."

While the Dempster move was posed as a hypothetical situation to Peavy, the right-hander stands firmly behind the starting rotation the White Sox presently have in place. Peavy believes Chris Sale is "the best pitcher in the big leagues" leading the White Sox staff, and looks at a guy such as John Danks as the equivalent of a great midseason addition for the South Siders when he comes back healthy.

The addition of Dempster still would help any team, in Peavy's mind, even as an AL debut after 15 years in the NL.

"If you can pitch, you can pitch. I don't care what league it's in," Peavy said. "And Ryan Dempster can flat out pitch, if we are going to speak on Dempster.

"He will be just fine doing what he's doing now in the AL. That's all there is to it. Will you give up an extra run or two? Maybe. Will there be a few less strikeouts because you don't face the pitcher? Maybe.

"At the same time, pitching is pitching and I know that there are some guys who might have a tough time. But Ryan Dempster is a bona fide front-of-the-rotation starter when he's right. He can pitch anywhere."

De Aza proving perfect for leadoff role

ST. LOUIS -- Since the start of June, Alejandro De Aza has played in 11 games and hit in 10 of them. He has a .387 average over a current seven-game hitting streak and has hit in 19 of his last 22 games going back into May, with 11 of those efforts being of the multihit variety. He hasn't gone hitless in back-to-back starts since May 17-18.

The success for De Aza might surprise some, considering the left-handed hitter's only everyday play came from his July 27 callup until the end of last season. It's all about taking advantage of this chance.

"Did I know? I don't know," said White Sox hitting coach Jeff Manto, when asked if he could have predicted De Aza's big numbers after working with him last year as the White Sox Minor League hitting coordinator. "If he had the opportunity, I was going to be interested to see what was happening. He has proven that he belongs.

"He's always on his feet. He never has a bad at-bat. From the first pitch to the last pitch of the at-bat, he always stays within himself and within his plan. His swing is so low maintenance that it's perfect for that leadoff spot.

"There's not a whole lot of timing issues there. There are not a whole lot of mechanical issues. It's an approach that can sustain itself throughout a season. And with his ability to bunt and run, it's a perfect spot."

Having 27 RBIs at the top of the order doesn't hurt the White Sox attack either. But De Aza's job is to work the count, get on base and set the table for RBI men such as Adam Dunn and Paul Konerko. So, his 45 runs scored and the four pitches he averages per at-bat are more important to the team than his RBIs.

"Historically, when you have a leadoff guy who can get on base, it brings a whole new dimension," Manto said. "It puts a lot of pressure on the defense and on the pitcher, and similarly, you are trying to be perfect to keep him off the bases.

"More times than not you make a mistake and the next thing you know, he's hitting a double. That position, especially how he does it, it's very important. He's not your typical slap guy. He definitely has some pop."

Third to first

• Alex Rios was ejected during the ninth inning of Thursday's 5-3 loss to the Cardinals by first-base umpire Jeff Nelson. Rios was ejected after he returned to the dugout following a flyout to center.

• Dunn launched a three-run homer in his return to the starting lineup in left field. Dunn rolled his right ankle on an eighth-inning homer in Tuesday's victory and was limited to an eighth-inning pinch-hitting role during Wednesday's loss. But he felt good enough to test his less painful but heavily taped ankle.

"After the way he jogged down the first-base line [Wednesday], he had to lobby his way in. He did some sprints down the hallway," said a smiling Ventura. "He's fine."

• White Sox starters are 6-2 with a 2.12 ERA and a .214 opponents' average against over their last 10 road starts. The White Sox lead the Majors with a 2.95 road ERA.