If he scores a touchdown Sunday, Seattle Seahawks running back Shaun Alexander will break the NFL record for touchdowns in a season with 28. Alexander is also the NFL’s leading rusher with 1,807 yards and is the consensus favorite to win the league’s MVP award.

Needless to say, Alexander’s great season will make him a hot commodity in the upcoming free-agent market. The one-year, $6.3 million contract he signed before the season includes an unusual clause, stipulating that the Seahawks cannot restrict his free agency by labeling him their “franchise player,”- meaning if the Seahawks want to retain Alexander’s services, they’ll have to outbid the rest of the league to do it. And to do that, they’ll likely have to offer him at least seven years for about $50 million.

As remarkable as Alexander’s statistics have been in Seattle – 7,744 yards and 88 touchdowns in six seasons – the Seahawks would be better off not giving him the multiyear, multimillion-dollar contract he has said he expects this off-season. Why? Alexander is an aging running back with a lot of tread on his tires, and all his accomplishments have been aided in large part by the Seahawks’ first-rate blocking.

An important factor that any team should consider when negotiating a contract with Alexander is his age. Alexander will turn 29 before the 2006 season, which might not sound old, but NFL running backs generally peak in their mid 20s. A long-term deal for a running back heading toward the downside of his career doesn’t make much sense.

Alexander has never missed a game in his career, so injuries wouldn’t seem to be a concern. But he already has 350 rushing attempts this year. With one more regular season game and as many as three playoff games ahead for the Seahawks, Alexander will probably have carried the ball upward of 400 times by the end of the postseason. Running that often takes its toll, and backs who carry the ball that many times frequently suffer injuries the following year. The latest example is the Jets’ Curtis Martin, who had an injury-plagued 2005 season after carrying the ball a career-high 371 times for 1,697 yards in 2004.

But the possibility that age and injuries will slow Alexander down isn’t the biggest reason to doubt he can continue at his current rate of success. The biggest question is whether his gaudy statistics are the result of his own ability or that of his teammates.

No running back in the league gets better blocking than Alexander. Three of the players who block for him – tackle Walter Jones, guard Steve Hutchinson, and fullback Mack Strong – were selected to the Pro Bowl. And Pro Bowl quarterback Matt Hasselbeck prevents opposing defenses from crowding the line of scrimmage to stop the run. If a struggling team lacking Seattle’s great offensive line and high-quality quarterback signs him, it might find out that Alexander can’t carry an offense by himself.

Moreover, the success of Alexander’s backup, Maurice Morris, indicates that Seattle’s offense could succeed if Alexander were elsewhere in 2006. Despite limited action, Morris has proven himself fully capable of running effectively behind the great Seattle line. He has 162 carries for 781 yards in his four-year career, an average of 4.8 yards per carry, which tops Alexander’s career average of 4.6 yards per carry.

Letting some other team pay Alexander a king’s ransom and keeping Morris as the full-time starter at running back next year might make the most sense for Seattle, but there is one complication – Morris is a free agent at the end of this season, too. But because Morris has yet to prove he can be an every down back, he won’t command anywhere near the salary that Alexander will. Running backs Deuce McAllister (New Orleans), LaDainian Tomlinson (San Diego), and Clinton Portis (Washington) have all signed eight-year contracts with signing bonuses of about $12 million and total values of around $50 million in the last two years.

Alexander has better numbers than any of those runners, so in 2006, he and his agent will tell teams that he wants to receive the league’s biggest running back contract. If that is Alexander’s demand, the Seahawks should walk away from their MVP – or rather, let him walk away from them.

Mr. Smith is a regular writer for FootballOutsiders.com.