If it ain’t broke, don’t fix it.

That’s the stance the Denver Broncos have taken in the face of critics and fantasy football owners who have questioned the team’s insistence on a running-back-by-committee approach since Clinton Portis left the team two years ago.

Denver’s thinking is that whoever best fits the zone-blocking scheme at a given time – be it before week two or during a goal-line situation in the Super Bowl – is going to get the call.

And that will mean a surprise for undrafted free agent and former Arizona star Mike Bell come the Broncos’ season-opener against St. Louis on Sept. 10.

Bell has fulfilled his end of the bargain since being named the starter over veterans Tatum Bell (no relation) and former Heisman Trophy-winner Ron Dayne before Denver’s first preseason game.

He outshined both of his main competitors in four contests, averaging more than five yards per carry and registering the team’s longest run (38 yards).

Although he fell imperceptibly short in yards and carries to newcomer Cedric Cobbs in the preseason, Bell has already been given the seal of approval from team management, and we’ve seen how generous the Broncos have been with giving out starting spots.

In 2000, the team gave the No. 1 job to a 26-year-old sixth-round pick named Mike Anderson, who went on to rush for almost 1,500 yards and be named the NFL’s Offensive Rookie of the Year.

It’s premature to suggest that Bell will end up have similar success this season, but it’s possible.

His shifty style of play is exactly what the Broncos want to see from their backs, and as far as they’ve been concerned, pomp can take a back seat to persistence.

The humble Bell, a longtime Broncos fan whose work ethic during practice has been well documented, should be more than happy to oblige.

What do past 1,000-yard rushers Olandis Gary and Mike Anderson and my grandma have in common?

Denver coach Mike Shanahan believes all three could be the starting running back for the Broncos.

Shanahan has become so cocky he thinks a guy who never rushed for more than 1,000 yards in a season in college and wasn’t even drafted can hold down the fort for a team vying for the playoffs. The tortoise can rush for 1,000 yards behind the Broncos’ offensive line.

Or maybe – and more likely – the clever ball coach is just dangling Mike Bell as motivation for the other Bell, Tatum, who ran for only 31 yards less than Mike in 27 fewer carries … in the NFL last season.

The zone-scheme running attack that has made Shanahan into a genius isn’t broke and shouldn’t be fixed. Tatum Bell, who averaged 5.3 yards per carry last season, isn’t broke either, so what’s the point of a quick fix?

Give Mike Bell his due for even making the squad after Shanahan cut his third-round pick last year – albeit it was Maurice Clarett – but let’s not anoint him the Broncos’ next Terrell Davis before he takes a single regular-season carry.

Bell’s shifty style doesn’t necessarily fit the Broncos’ straight-ahead attack. Although Bell has great vision, according to UA offensive coordinator Mike Canales, his east-west running style doesn’t fit the north-south Mike Anderson-type attack that produced more than 1,000 yards last season.

Don’t forget, Bell wasn’t even the best rookie running back for the Broncos this preseason. That honor belongs to Cedric Cobbs, who had more carries and yards.

By all accounts, Bell’s attitude was nothing short of sensational in training camp and his humble nature will fit perfectly in the locker room, but when it comes to starting on a contending playoff team, it’s not about attitude, it’s about numbers.

Just ask Terrell Owens.