BOSTON -- Monday marked the seventh game in a row that leadoff man Jacoby Ellsbury was not in the Red Sox's lineup. The left side of his chest, which endured Adrian Beltre's knee in a collision on April 11, is still sore. The club is hoping that Ellsbury can return at some point during its three-game series against the Rangers, which starts on Tuesday night, but that no longer seems like a certainty.

When does Ellsbury think he will return?

"I'd like to make a prediction, but it's kind of hard to tell," Ellsbury said after the Red Sox's 8-2 loss to the Rays. "I wish it would have been a little bit quicker, but this is one of those things that needs rest."

Boston manager Terry Francona said that the club will try to ramp up Ellsbury's hitting program on Tuesday, which should be a tell-tale sign of whether an imminent return is realistic. If not, the Sox could come to the determination that they are best off putting him on the retroactive disabled list. In that case, he would be eligible to return for the April 27 game in Toronto.

Josh Reddick, who spent multiple stints with the Sox last year and was a stand-out performer in Spring Training this year, would be the logical candidate to be recalled from Triple-A Pawtucket if Ellsbury goes on the DL.

The Red Sox are 1-6 since Ellsbury went down.

"You're part of the team," Ellsbury said. "You want to be out there and contribute, but it's just a rough stretch right now. We'll get out of it."

Lack of command leads to Lackey's first loss

BOSTON -- John Lackey prides himself on being that guy his team needs to stop a losing streak. That's why bulldog has been the word most often associated with the big right-hander throughout his career. And that's also why Monday's 8-2 loss to the Rays was so difficult for Lackey to stomach.

In his three starts for Boston, this was the first time he has taken the ball with his team reeling. And he could not come through, giving up nine hits and eight runs over 3 1/3 innings in the defeat that completed a four-game sweep at the hands of Tampa Bay.

"It was an opportunity to [end a losing streak], and I obviously didn't get it done," said Lackey, who is 1-1 with a 5.63 ERA.

The problem was location.

"[My] fastball location wasn't there," Lackey said. "I was hitting the white part of the plate quite often. That's not good."

When he went to his other pitches, that didn't work either.

"[I] tried to mix up some things, but I fell into a couple patterns with my breaking ball, which wasn't good," said Lackey. "They're a good team. They swung the bats well today -- you've got to tip your hat sometimes, but I definitely put myself behind in some counts and didn't execute when I needed to."

The loss put the Red Sox at 4-9, their worst start since 1996. They are six games behind the Rays and 5 1/2 behind the Yankees in the American League East.

"Obviously it hasn't been good," said Lackey. "But I have enough to work on myself, today, before I start talking about anyone else on our team. Hopefully we'll get it all out of our system now and get on a little roll here."

Cameron dealing with more abdominal pain

BOSTON -- Mike Cameron was originally in Monday's lineup against the Rays, but the center fielder was scratched when he started experiencing lower abdominal pain similar to last week, when he was in the process of passing a kidney stone.

Before the game, the Red Sox suspected the center fielder might have been on the verge of passing more kidney stones. But after its 8-2 loss to the Tampa Bay, Boston still trying to get a handle on what was ailing him. Cameron was sent to Massachusetts General Hospital prior to the game.

"He's been there all day," said Red Sox manager Terry Francona. "The CT scan, we think, ruled out more stones. He's in a tube now. They've got multiple doctors trying to figure out what's going on. We don't know. He's been in there all day."

The kidney stone issue initially developed for Cameron on Thursday in Minnesota, where he was a late scratch for that afternoon's game. He was back in the lineup on Saturday, but Cameron felt a little sluggish in Sunday afternoon's game.

"He didn't feel great, but I think he thought it was more general soreness from sitting for a few days," Francona said. "And I think he's probably a tougher kid than people realize. I haven't had what he's going through, but when you talk to people that [have had kidney stones], they say it's agonizing. And he's out there playing."

Cameron's health issues could explain why he hasn't looked as polished on defense as normal. He is also getting re-acclimated to American League parks. A three-time Gold Glover, Cameron made an error on Saturday night and seemed to get a late jump on a fly ball on Sunday that turned into a double.

"I think there's a couple things," Francona said. "I don't think, physically, that he's felt great the past week. He's been in Minnesota, and that's a new ballpark for everybody. Fenway certainly is, for him. So yeah, I don't disagree with that. We haven't been on the field very much [because of day games]. I'm not making excuses, but yeah, I'm sure he is [getting adjusted]."

Hall trying to get re-acclimated to center

BOSTON -- When the Red Sox acquired Bill Hall, they were excited about the fact he could play three infield positions and the corner-outfield spots. Because of the way their roster shaped up, they didn't expect to need him in center field, and therefore didn't have him work out there in Spring Training.

As it turns out, Mike Cameron (lower abdominal pain, kidney stones) and Jacoby Ellsbury (left rib contusion) have been banged up at the same time, putting Hall in position to make his third start of the season in center on Monday.

There were some challenging plays in the 8-2 loss to the Rays that didn't go his way. In pursuit of B.J. Upton's deep fly ball to right-center in the third, Hall raced to the Boston bullpen, but he ran into the short wall, having the ball tick off his glove for a three-run homer. An inning later, he misplayed the carom on a triple by Jason Bartlett.

Hall has started three games in center, marking his first three starts there since 2006, when he was with the Brewers.

"It's tough," said Hall. "Coming into this season, center field is probably the last place that I thought I would have to go and play. I knew I was going to play a couple times this series. I didn't know I was going to play today until this morning, obviously, but it was raining all series, so I didn't get to get out there. There's a lot of things going on in center field, in the outfield, period. Practice is where you learn. I didn't get a chance to get out there."

Fenway Park has one of the most challenging center fields in baseball.

"But that ball [that Upton hit out], I don't think the field played anything into how I went after that ball," Hall said. "But balls off the wall, you've got to learn how they come off, the angles off the wall. There's just a lot of stuff out there. It takes a little time."