BOSTON -- Red Sox starter Clay Buchholz threw 30 pitches in a successful side session before Monday's series opener with the Royals and said his back feels about 80 percent, a healthy improvement from the constant pain he's reported since landing on the 15-day disabled list June 17.

"I think it's going to feel better," Buchholz said. "There was still a little soreness coming off after I threw. [I] sat down for about 10 minutes, did a couple stretches and it felt better. This is, I think, the biggest step in the right direction so far in this process."

"The ball came out of his hand great," said manager Terry Francona. "If you watched him throw, you would never believe he's missed time. It's just exploding out of his hand."

Buchholz threw mostly fastballs while mixing in a few curveballs, changeups and cutters. He'll take the day off on Tuesday and hopes to throw a full bullpen session on Wednesday.

"I don't know how quick they'll want me to jump back into things, but I think a lot we'll be able to take away from the next one off the mound," he said. "I want to do it as quick as possible. I think it's going to take a couple starts getting back into it, facing live hitters, probably go a couple innings at a time, and see how it feels from there."

While he's been throwing with back pain for a majority of this season, Buchholz said he was at about 30 percent during his last bullpen session in Philadelphia at the end of June and is feeling closer to 80 percent this time around. He's been told he has no structural damage and it's just a pulled muscle, so he'll continue to pitch through the pain as doctors don't believe it will risk further injury.

"I want to be ready to go," he said. "If it's in the middle of August, that's good. If it's September, that's good, too. I want to be able to come back and help this team get to the postseason and work our way from there."

Drew headed to 15-day DL; Weiland optioned

BOSTON -- Red Sox outfielder J.D. Drew appears ticketed for the 15-day disabled list on Tuesday with a left shoulder impingement.

Manager Terry Francona said Monday that Drew would be placed on the DL in a corresponding move with the activation of starter Jon Lester, but instead the club optioned right-hander Kyle Weiland -- who Francona originally said would work out of the bullpen -- and will likely send Drew to the DL on Tuesday.

"There's a lot of moving parts," Francona said after Monday night's 3-1 loss to the Royals in 14 innings. "Some of it is baseball, and some of it is personal. We got caught in some things that I'm probably not able to talk about. You're going to have to take my word for it that sometimes personal stuff gets in the way."

Drew's left shoulder has caused him discomfort and reduced strength, Francona said. The outfielder had been getting treatment for the last few weeks and hasn't appeared in a game since last Tuesday. He had an MRI on Saturday.

"We didn't DL him right away because we didn't have a move we wanted to make, and we could have pinch-ran him or something like that," Francona said. "Hopefully a couple weeks down will do him some good. He can get some strength back in that shoulder. Maybe we'll have a better chance of seeing that J.D. that we're hoping for."

Drew had been hitting just .219 through 233 at-bats this season, smacking four home runs and six doubles and slugging just .305, more than 100 points less than his previous career low. This will be the 35-year-old Drew's second trip to the DL as a member of the Red Sox, the other occurring in 2008 when he missed 37 days with a cartilage injury in his back.

The hot-hitting Josh Reddick has gotten the majority of at-bats in right field lately, as he continues to provide some spark with a .366 average. The 24-year-old Reddick has been aware of the trade rumors swirling around Boston, indicating the club could add another outfielder to the mix, but he said he's trying to stay focused on what he can control in his third season of Major League action.

If Drew does get placed on the DL on Tuesday, the Sox appear likely to replace him with utility man Drew Sutton, who hit .298 over 26 games with Boston this season, playing all over the infield and two games at left field.

Even after the bullpen combined to throw 8 1/3 innings in Monday's loss, Francona said the club doesn't need another pitcher just yet.

"[Alfredo] Aceves has got a day off [after throwing 46 pitches Sunday]," the skipper said. "We stayed away from him tonight. He can give us length. Everybody else probably is available. I think we're OK."