01:00 AM EDT on Tuesday, May 17, 2005

BY SEAN McADAM
Journal Sports Writer

OAKLAND -- Though the exact nature of the injury remains something of a mystery, outfielder Trot Nixon expects to undergo surgery on his right leg at the end of the season, meaning the Red Sox will have to monitor him for much of the remainder of the season.

Nixon told the Boston Herald that the unspecified problem will require surgery. He said the injury dated back to the team's doubleheader against Seattle on Mother's Day at Fenway Park.

The outfielder was taken out of the game in the late innings Saturday at Safeco Field and replaced in right by Jay Payton , an inning after his grand slam helped the Sox grab a lead against the Mariners.

Nixon declined to speak to reporters yesterday before the Sox began a series with the Oakland A's. Citing player confidentiality issues regarding injuries, manager Terry Francona would not elaborate on Nixon's condition.

"We monitor everything," he said. "Trot's no different. We want to help him when we can (in terms of giving him some time off) so he's able to be productive."

Francona added that Nixon's comments Sunday won't change the team's approach to him.

"I'm not sure it changes anything," he said.

Nixon likely will sit tonight when the Sox face left-hander Barry Zito . The right fielder is off to a terrific start, batting .337 -- the highest average among regular position players on the Sox -- with six homers and 24 RBI. His slugging percentage (.592) is second only to David Ortiz 's (.593), and his on-base percentage of .444 is tops on the club.

Wells set to go

David Wells had a brief 20-minute side session in the Red Sox' bullpen yesterday, and Sox officials confirmed that Wells is set to start the final game of the road trip tomorrow.

Wells will bump Jeremi Gonzalez , who's made three starts for the Sox with Wells and Curt Schilling sidelined.

The veteran lefty has been out with a foot injury since April 26.

Appeal may be dropped

Though the club wouldn't officially confirm it, indications were that last night's starter, Bronson Arroyo , was planning to drop the appeal of his six-game suspension stemming from the brawl against Tampa Bay on April 24.

If Arroyo sits out the next six games, he would next be eligible to pitch in Toronto on May 25.

The timing is good for both Arroyo and the Sox, since they have an off-day Thursday and another "day off" Monday, when they have an exhibition game against Detroit in Cooperstown, N.Y.

That means Sox could get by with four starters until Arroyo comes back form his suspension.

Hall of Fame Game

The Sox are in the process of putting together a roster for the Hall of Fame Game Monday against the Tigers.

Francona will have most of the regulars in the starting lineup for an at-bat or two, though he indicated it is doubtful Manny Ramirez and Jason Varitek will play.

Of greater concern is the pitching staff. The Sox plan to bring in minor-league pitchers for the game, though Francona was unsure who would get the starting assignment.

One problem is a matter of timing. None of the Sox' affiliates has an off-day, meaning players will miss games.

The exhibition game takes place before the Sox embark on a six-game trip to Toronto and New York.

Around the bases

Infielder Ramon Vazquez , who has been nursing a sore quad and hasn't played since May 8, was cleared to return to action by the training staff yesterday. . . . Statistical oddity: 12 of Mark Bellhorn 's 24 hits have been doubles.