Sweeney was eligible to come off the Oakland A's disabled list on Monday but isn't quite ready to play after undergoing surgery on both knees. He's been out since May 28.
"I'm feel like I could swing a bat right now and jump in a game, but when I do get back, big Frank [Thomas], the Hall of Famer, is going to be chewing up at-bats [as the designated hitter] so I've got to be a full player," Sweeney said.
"They want me to play first base. So I'm going to go to rehab on Thursday, go to Sacramento and play five or six games and make sure my body could put up with it and make a decision then."
As Sweeney was running the bases on Monday, he let out a yelp and slowed to a stop. He was limping on his left knee. That was an indication that he's not out of the woods yet.
"It's loss of cartilage there. There's just bone, no cartilage, which is why I had the 'yeow!'" Sweeney said.
Three doctors have told him he still needs microfracture surgery on both knees, similar to that undergone by Greg Oden of the Portland Trail Blazers.
The problem is there's a long period of recovery, as much as a full year on one of his knees.
"So the question is, when do I do it?" he said.
Another question is, can he continue to play on his knees as they are now?
"That's what I think I'll figure out this next week or so when I'm on rehab assignment," he said. "It's fairly easy to hit BP and run straightaway sprints in tennis shoes on the grass but running the bases, as I saw today, is a little tougher."
Thomas, also working back into shape from a quad injury, told Sweeney to go ice his aching knee. Sweeney said he would, right after he fielded some ground balls. He is, as usual, very determined.
"So we'll see how it all turns out," he said. "I'll make it back. As my wife can tell you, I'm a hard-headed Irishman."
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.