That apparently includes the Bears, who might rely on as many as four players to replace Harris, who suffered a sprained left medial collateral ligament last week and was diagnosed Monday with a torn left hamstring that will require surgery, for Monday night's game against the St. Louis Rams.
Harris will undergo surgery in Dallas and be placed on injured reserve, ending his season.
While much of the attention leading up to the game has focused on whether Smith will replace quarterback Rex Grossman if he continues to struggle -- sources have indicated a switch to veteran Brian Griese could come at halftime if Grossman has a rough opening two quarters -- the question of compensating for the loss of Harris has been largely overshadowed.
But the Bears clearly plan to deploy a committee approach at the "under" tackle vacancy created by the absence of Harris, who was playing at a Pro Bowl level before suffering the leg injuries in last week's victory over the Minnesota Vikings. Who plays when, and how the tackle rotation evolves, will mostly be based on game circumstances as the Bears coaches try to cobble together a Frankenstein monster-type replacement for Harris.
"We're going to roll a lot of different people into that spot," acknowledged starting right defensive end Alex Brown, who figures to move inside to tackle on passing downs. "It's going to be a challenge. But Tommie did so many things, really, that we're all going to have to combine to fill all those roles."
The likely starter at the "under" tackle spot, where a defender is aligned to the outside shoulder of the guard across from him, is six-year veteran Alfonso Boone. A 318-pounder who doesn't have the quickness of Harris, but has demonstrated some penetration skills in the past, Boone has been a spot starter in the past. He will probably play on the running downs and could be spelled by Ian Scott and Antonio Garay.
Scott started 13 games in 2005 and opened this season as the starting nose tackle before being bumped from the lineup by Tank Johnson after three games. A second-year veteran, Garay has appeared in just one regular-season game in his career, but has impressive physical skills, and could become part of the tackle rotation now, with Harris ailing.
It is Brown, however, who might have to make the most difficult adjustment. The former University of Florida star is accustomed to playing on the outside, where his upfield burst has netted him six sacks this season, but will now find himself operating in much more traffic on third down. Plus, at only about 260 pounds, he could be giving away 40-50 pounds to the Rams' offensive guards.
"Everything is much faster [at tackle]," Brown said. "People are on you immediately. You've really got to use your hands, get them up quick, to keep [blockers] from locking on you. It's just a completely different game in there, but Tommie was a different guy, and that's why he was so good at it."
Len Pasquarelli is a senior NFL writer for ESPN.com. To check out Len's chat archive, click here.