Gardner suffered his injury sliding into second base to break up a double play against the Athletics. He originally thought the injury was a jammed thumb, but the ligament pulled a piece of bone off his thumb.
"Everything felt well," Garnder said of his rehab assignment in Triple-A. "The only thing I was really worried about was my hand, my finger, because everything else -- I was able to stay in pretty good shape. My legs feel good, everything felt good."
Gardner's arrival allowed manager Joe Girardi to use Melky Cabrera in left field and spell Johnny Damon. Eric Hinske started as the designated hitter.
"It allows you to move some of your outfielders around and give them a day, as well," Girardi said. "If a guy is banged up, we can give him a couple of days off. Melky has played extremely well for us and has played every day. Melky could probably use a day here somehwere."
At the time of his injury, Garnder had appeared in 77 games, hitting .275 with a .354 on-base percentage. He has 20 stolen bases in 25 attempt this season.
"He brings back, No. 1, a player that has the ability to change a game, just by being on base, with his speed," Girardi said. "All players have attributes, that are above average in certain areas. And he really has one."
Gardner said he hoped his rehab assignment helped him get his timing back, and he wasn't worried about results.
"I was struggling to get some hits and find some holes," he said. "I told the guys I was trying to save my hits, so hopefully, I've got some saved up in me."
Duncan hit .221 with eight homers and a .299 on-base percentage in 57 games with the Yankees between 2007-08. His 2009 performance at Scranton/Wilkes-Barre -- he hit .277 with 30 homers -- helped him earn the International League's Most Valuable Player award.
"We decided this morning, actually," Girardi said. "He provides us some coverage at some different positions. You can play him in the outfield. You can him play him at first if you had to. You can DH him if you want to. Physically, this is a grind for guys."
Duncan was summoned from Scranton, Pa., and though he wasn't guaranteed to be at Yankee Stadium by the first pitch, Girardi said he would be eligible for the opener.
"He may not be here for the anthem," Girardi said. "He won't get fined, though."