Roy Jones Jr. took Saturday night's fight against journeyman Glen Johnson as a tuneup for a possible rematch with Antonio Tarver. He left the bout at the FedEx Forum in Memphis in an ambulance, headed to the hospital with a concussion following a second straight devastating knockout loss that could spell the end of the 35-year-old's career in the ring.

There was plenty of speculation by boxing insiders yesterday that Jones (49-3) will retire. A champ at four weight classes -- from middleweight to heavyweight -- the opposition finally seems to have caught up to Jones. The loss to Johnson, also 35, was stunning -- especially considering Johnson (41-9) had won only two of his previous five bouts.

"That's two devastating knockouts in fights he was supposed to win," Hall of Fame trainer Emanuel Steward told the Memphis Commercial Appeal yesterday. "I don't think he has any choice but to retire."

Now, Johnson and Tarver, who took the WBC title from Jones in May -- after Jones had taken it from him -- are talking about a fight of their own.

Johnson Also Dethroned

Jones wasn't the only champ to lose his belt in Memphis. Washington 115-pounder Mark Johnson (44-4) was knocked out at 2 minutes 40 seconds of the eighth round by Ivan Hernandez. The loss, the first in Johnson's career to come by knockout, cost Johnson his WBO title. . . .

The Memphis card also featured the pro debuts of brothers Lamont and Anthony Peterson, both of whom had touted amateur careers before falling short of qualifying for the Olympics earlier this year. Anthony Peterson, at 135 pounds, scored a first-round knockout of Toris Smith (1-15); Lamont Peterson, at 140 pounds, stopped Nicholas Dean (0-2) in the second round. . . .

Michael's 8th Avenue in Glen Burnie, which has developed a well-earned reputation as the site of one of the best club shows in the country, hosts a seven-fight card Thursday.