Tomlin did allow that Lacy is "top-notch" but explained that the Steelers loved Bell's versatility as a three-down back with elite receiving skills.
What Tomlin did not acknowledge is that Lacy's surgically repaired toe was a factor. The Pittsburgh Post-Gazette reported last April that the Steelers' front office "would not touch" Lacy because his big toe had been fused prior to his senior season at Alabama. Pittsburgh wasn't the only team concerned about the long-term effects of that surgery.
Anyone who has watched him bulldoze opponents this season realizes the latter is a non-factor. He leads the league in rushing yards after contact, according to ESPN Stats & Info.
Lacy is seventh in the NFL with 1,028 rushing yards. He's just 77 shy of breaking John Brockington's 1971 Packers record for most by a rookie.
Bell is no slouch himself. He's already emerged as one of the most effective pass-catching running backs in the NFL. On the flip side, he's averaging just 3.3 yards per carry.
There's no reason to doubt Tomlin's preference for Bell, but it might very well have more to do with Lacy's medical file than the game film.