NEW YORK -- Desmond Jennings underwent an MRI exam on his left knee on Monday, and the results showed a sprain.

"I was hoping [the MRI] didn't come back with nothing," said the Rays left fielder. "But if it was anything, that was probably the best thing. It's not a good feeling either way, but I can live with what it is."

On Tuesday, Jennings was not in the Rays starting lineup against the Yankees, but he doesn't believe he'll be on the shelf for long.

"Feels better -- feels better than it did," Jennings said. "Every day. It's gotten better the last couple of days."

Jennings, who is hitting .270 with three home runs and 11 RBIs, left Sunday's game in the second inning, shortly after sliding into home; he then ran slowly to first base. Jennings now believes that the slide caused the injury.

"I didn't feel it right away," Jennings said. "I went back to the dugout and sat down a minute. I got up and I just slid in home, so I figured I was just a little sore. Then I went out to the outfield, and it didn't feel good.

"[I felt sore] before [running to first base], and I just figured something was up. I just didn't want to mess it up more than what I thought it was already. I didn't want to do too much on it to make it worse."

When asked if he would be available on Tuesday night against the Yankees, Jennings said: "I don't know, but probably not."

Jennings also told reporters that he has injured his right knee in the past.

"Yeah, I hurt my meniscus in my right knee a few years ago, but nothing close to the feeling of this," Jennings said. "That was way worse."

Jennings sounded adamant that his injury will not be a long-term concern.

"I don't think I'll have to go on the DL," Jennings said. "I don't plan on going on the DL. I don't think it's that bad."

Rays manager Joe Maddon held out hope that Jennings might be available for pinch-hitting duty on Tuesday night. Jennings was asked when he might play again.

"Hopefully Wednesday," Jennings said. "I really don't know."

Keppinger to restricted list; Rays add Guyer

NEW YORK -- Following Tuesday night's 5-3 loss to the Yankees, the Rays placed Jeff Keppinger on the restricted list due to a personal matter and recalled outfielder Brandon Guyer from Triple-A Durham.

Keppinger, who signed with the Rays as a free agent on Jan. 26, started at third base on Tuesday night and went 1-for-3 to raise his average to .313 for the season. The club believes Keppinger's absence will be short term.

Rays manager Joe Maddon explained the move.

"What it does is just gives us another right-handed bat for now," Maddon said.

Guyer was hitting .294 with three home runs and 13 RBIs in 22 games for Triple-A Durham.

Maddon sees improved swings from Upton

NEW YORK -- B.J. Upton entered Tuesday night's game against the Yankees with three extra-base hits and three RBIs in his last three games, batting .333 overall. Upton was hitting .387 (12-for-31) in his last eight games.

"I've seen a more aggressive swing," Rays manager Joe Maddon said when asked about the difference in Upton. "I've seen the bat head out front. I'd say that's primarily the difference, that it's a better, more aggressive swing. From my side at the first-base side at [Tropicana Field], you can see the better extension, and just more of an aggressive, committed swing -- that's what I'm seeing."

The Rays are 12-4 since Upton was activated from the 15-day disabled list on April 20. He missed the first 13 games with lower back soreness.

Extra bases

• Maddon said he talked to Don Zimmer on Monday. The Rays senior advisor has been experiencing a myriad of health problems lately, but Maddon said Zimmer was doing a lot better.

"The sound of his voice was a lot stronger," Maddon said.

• On Wednesday, David Price, James Shields and Sean Rodriguez will visit the MLB Fan Cave at 11 a.m. ET.

• Double-A Montgomery outfielder Kyeong Kang was named Southern League Player of the Week after hitting .429 with four home runs, seven RBIs, two doubles and 11 runs scored in six games.

• The Rays' current road trip opens with three games against the Yankees, followed by three against the Orioles before wrapping up with two against the Blue Jays. The club will then return home to play two against the Red Sox. Rays players understand the significance of the treacherous early-season stretch.

• "I think this is a huge road trip, especially being pretty early in the season," right-hander Jeff Niemann said. "Facing three division rivals [on the road] and seeing how we shape up. ... It's about 10 days, two weeks of it. It's a big two weeks coming up, and hopefully we keep playing well."