How well an NFL team is able to successfully replace injured starters with backups is always critical in the league.
On Monday night in Denver, the Steelers were without three starters on defense because of injuries or organizational diligence. The short-handed condition didn't hinder the team's performance.
Safety Tyrone Carter was cited as the AFC defensive player of the week for registering two interceptions, including one returned for a touchdown, and two other passes defensed in the Steelers' 28-10 victory. Technically, Carter wasn't starting for an injured player because free safety Ryan Clark was held out of the game over concerns about how his sickle cell trait would respond in the Mile High City's thin air. But Carter is used to solving problems in the Steelers' secondary. The 10-year veteran started four games at strong safety earlier this season when Troy Polamalu was sidelined by a sprained medial collateral ligament.
Special-teams ace Keyaron Fox, starting at inside linebacker for Lawrence Timmons (ankle), had seven tackles, with one for a loss. End Nick Eason, starting for Travis Kirschke (ankle), who had already replaced standout Aaron Smith (season-ending shoulder injury), added a tackle.
On offense, tailback Rashard Mendenhall, who won the starting job when Willie Parker went down with a toe injury a month ago, rushed for 155 yards. On many of his 22 carries, Mendenhall ran behind right guard Trai Essex, who has started all eight games because of a season-ending knee injury to Darnell Stapleton.
"It's what being a team is all about," said Clark, who was ruled out of Monday's game by coach Mike Tomlin. "Everyone stepped up big and contributed, and that's a tremendous tribute to us having so many guys on this team who are ready to play. When your number is called, be ready."
Not every team in the league, of course, survives the kind of attrition that has struck the Steelers in recent weeks. Yet Indianapolis has lost three-quarters of its starting secondary to injuries, and the Colts remain undefeated. Ditto for the New Orleans Saints, who have played the entire season without two-time Pro Bowl left tackle Jammal Brown (hip), with starting defensive tackle Sedrick Ellis (knee) out of the lineup for the past two weeks and likely to be absent for at least two more, and defensive tackle Kendrick Clancy (knee) lost for the rest of the season.
Philadelphia remains in the NFC East race despite playing the entire season without two-time Pro Bowl offensive lineman Shawn Andrews (back) and three games absent standout tailback Brian Westbrook (ankle, concussion). The Eagles haven't been so fortunate at middle linebacker, where they are on their third different starter after losing Stewart Bradley to a knee injury in the preseason.
For our purposes, we are primarily concentrating on those players who in the first half of the season started at least four games because of injuries. There have been, of course, some strong performances from players who started fewer than four games: New England offensive tackle Sebastian Vollmer, Seattle linebacker David Hawthorne, Eagles tailback LeSean McCoy, among others.
But from the burgeoning group of players who have started four or more games in relief, there have also been some disappointments. Giants safety C.C. Brown was benched last week because of his play while replacing injured starter Kenny Phillips (knee). In San Diego, Scott Mruczkowski and Ogemdi Nwagbuo have played pretty well, but haven't been able to fill the holes created by injuries to center Nick Hardwick (ankle) and nose tackle Jamal Williams (knee), respectively.
Likewise, New York Jets nose tackle Sione Pouha has been decent, but he is not Kris Jenkins (knee). The Bears haven't been able to find an adequate replacement for middle linebacker Brian Urlacher (wrist).
As in past years, 2009 has experienced its share of super subs and replacement flubs, and it definitely has made a difference in the standings.
Len Pasquarelli is a senior writer for ESPN.com.