As the combination of knee surgery, age, and getting the ball more than 4,000 times in his NFL career combine to push running back Curtis Martin toward retirement, the Jets will need to examine the limited options available to them to replace their all-time leading rusher.

Martin hasn’t officially declared whether he’ll return for a 12th NFL season, but despite his assertion yesterday that he still wants to play, retirement looks increasingly likely.

Yesterday, the NFL’s no. 4 all-time leading rusher said he is working out every day so he can come back as quickly as possible, and is hopeful he can play in the season opener September 10 at Tennessee. But he made no guarantees about when his injured right knee will allow him to resume his career.

At 33, Martin is old for a running back, and he’s coming off his worst season, in which he had career lows in carries (220), yards (735), and yards per carry (3.3). Most troubling, Martin hasn’t healed from the knee injury that plagued him last season and forced him to have surgery in December. Martin is on the physically unable to perform list, meaning he can’t practice in training camp.

When the Jets open their preseason schedule Friday night in Tampa Bay, they’ll get their first look at what the offense might look like without the running back who has started all but five games in the last eight years.Three current Jets will compete to replace Martin in the backfield, but none has done enough to make the Jets confident that the team can have a competent running game.

Derrick Blaylock signed a five-year, $11.1 million contract as a free agent from the Kansas City Chiefs last year for the express purpose of becoming the heir apparent to Martin. But he did next to nothing last season, suffering a broken foot and gaining only 53 yards on 17 carries.Blaylock is the most experienced back on the Jets’ roster, which means he’ll almost certainly make the team. But if he can’t show more in training camp than he did last season, the Jets might have some thoughts about releasing him, despite the $3.2 million signing bonus they gave him last year.

Cedric Houston was the Jets’ sixthround draft pick last year and probably has the best chance to replace Martin as the starter. He showed some promise as a rookie, gaining 302 yards on 81 carries and earning the starting job when Martin’s knee forced him to miss the last four games. But Houston was prone to injury in college at Tennessee, and it’s unlikely that the Jets think he can stay healthy for a full season as a featured back.

Leon Washington, the Jets’ fourthround draft pick this year, will see significant playing time throughout the preseason. Washington is a good athlete, but few observers see him as the type of player who can step in and become an immediate starter as a rookie. Washington is more likely to be a special teams contributor and play only sparingly on offense.

Unless Blaylock, Houston, or Washington can impress the Jets’ coaching staff during the preseason, the team will have to consider trading for a veteran running back to take over the starting job. The most frequently mentioned candidate is Chris Brown, the Tennessee Titans’ starter for the last two years. Brown is a speedy player with a straightahead running style who looked like one of the league’s most promising young backs in 2004, when he ran for 1,067 yards on 220 carries. But last year Brown’s production diminished significantly, as he gained 851 yards on 224 carries, and this year he has said he would rather be traded than have to compete with veteran Travis Henry and rookie LenDale White for playing time. The Jets would love to acquire Brown, but the Titans say he’s not available.

Few other options exist if the Jets want to trade for a running back. The Arizona Cardinals, who signed freeagent running back Edgerrin James this off-season, might consider trading one of their backups, Marcel Shipp or J.J. Arrington. But neither Shipp nor Arrington is likely to step in and become a starter. Other running backs the Jets would consider trading for include Julius Jones and Marion Barber of the Dallas Cowboys, Michael Turner of the San Diego Chargers, and Thomas Jones of the Chicago Bears, but the Jets would have to give up a high draft pick to get any of those players.

The meager list of available running backs will lead to some inevitable second-guessing about whether the Jets should have drafted a running back in the early rounds of this year’s draft. Specifically, the Jets chose center Nick Mangold with the 29th overall pick, one slot before the Indianapolis Colts selected LSU running back Joseph Addai.Jets fans are mainly known for booing draft picks on the day of the draft, but they might have some retroactive boos for their front office if Addai becomes a topnotch player for the Colts.

But it’s unrealistic to think Addai — or any rookie — could fill Martin’s shoes. Martin hasn’t often made the type of spectacular runs that show up on “SportsCenter,” but he is one of the most dependable backs in league history. He is one of only three players (along with Emmitt Smith and Barry Sanders) who has rushed for 1,000 yards in 10 consecutive seasons. Perhaps more impressively, Martin has 3,518 career rushing attempts, 484 career receptions, and only 29 career fumbles.That rate of one fumble for every 138 touches is the best mark of any running back in NFL history.

If Martin has played his last game, he’ll be eligible for the Hall of Fame in 2011. Martin deserves a place in Canton, but he could have trouble getting there in his first year of eligibility. His competition on the Hall of Fame ballot will include running back Jerome Bettis, who retired in February after winning the Super Bowl with the Pittsburgh Steelers, and possibly two other backs, Marshall Faulk of the St. Louis Rams and Priest Holmes of the Kansas City Chiefs, who are recovering from injuries and considering retirement. Three perennial Pro Bowlers at other positions, offensive lineman Willie Roaf, linebacker Junior Seau, and defensive back Deion Sanders, have also retired this off-season. Martin shouldn’t have to wait before getting into the Hall of Fame, but that might be fitting for a great player who has always been underappreciated.

Mr. Smith is a contributing editor for FootballOutsiders.com.