ORCHARD PARK, N.Y. -- As Buffalo Bills players walked off the field Thursday, defensive tackle Kyle Williams teased quarterback Derek Anderson that the gray T-shirt he wore under his No. 3 jersey hardly showed any signs of sweat after a 90-minute practice.

In a perfect world, Anderson's uniform will stay in pristine condition for the remainder of a season in which the 14th-year veteran is expected to mentor rookie Josh Allen from both the sideline and in the meeting room.

"I’ve seen a lot of football -- I’ve been through a lot of ups and downs in my career and just be a guy that he can lean on," Anderson said Wednesday, one day after the veteran signal-caller signed a contract with the Bills. "[He can] ask me any question."

Beyond serving as the sage of the quarterback room, what would it take for Anderson to be pressed into duty as the starter? Other than an injury to Allen, it is hard to say at this point.

For now, the bigger question is whether Anderson is capable of being Allen's backup. Bills coach Sean McDermott said Wednesday that Nathan Peterman will continue as the team's No. 2 quarterback, meaning Anderson likely will be inactive when the Bills travel Sunday to play the Houston Texans. However, McDermott considered the topic a "crystal ball question" in which he could not predict the future.

Anderson overtaking Peterman for the primary backup job to Allen -- and being on the active 46-man roster for games -- likely would require Anderson proving worthy of the role in practice after he spent training camp, the preseason and the first quarter of the regular season out of football.

Anderson, 35, should have a shot at earning the No. 2 job over Peterman, who has been statistically one of the worst quarterbacks in recent NFL history. Peterman's 4.6 Total QBR is third worst among the 177 quarterbacks to start games since ESPN began tracking Total QBR in 2006, while his 16.8 passer rating is fourth worst among the 231 quarterbacks to start games since 2001.

Anderson was last a starter in 2010 for the Arizona Cardinals, when he completed 51.7 percent of his passes in 12 total games for 2,065 yards, seven touchdowns and 10 interceptions. In 2009, he started seven games for a Cleveland Browns offense directed by current Bills offensive coordinator Brian Daboll, completing 44.5 percent of his passes for 888 yards, three touchdowns and 10 interceptions.

The Bills were clearly attracted more to Anderson's experienced voice and its value to Allen than Anderson's résumé on the field.

"[Anderson's] primary role at this point is to add his wisdom in on and off hours when coaches aren’t always around and share his perspective on things with some young quarterbacks in that room in Nate [Peterman] and Josh," McDermott said Wednesday.

However, the key part of McDermott's statement -- and one that could invite speculation that Anderson has a shot to start for the Bills this season -- was his qualification that Anderson's primary role at this point is to be a mentor.

If Anderson leapfrogs Peterman for the Bills' No. 2 job in the coming weeks, he would take the field if Allen suffered an injury.

The risk for Allen to get hurt is real. He has been sacked a league-high 19 times this season and has run 31 times, the third most of any quarterback. Allen emerged unscathed from his hurdle of Minnesota Vikings linebacker Anthony Barr in Week 3 and from three diving touchdown runs this season, but a 2013 knee injury to Bills first-round quarterback EJ Manuel -- which wiped out the next four games of his rookie season -- should serve as a cautionary tale.

If Allen stays healthy and Anderson becomes the No. 2 quarterback, would Buffalo consider making Anderson its starter at some point?

For that to happen, the Bills would have to deem it untenable for Allen to remain under center and in the spotlight. Given that futures for first-round quarterbacks are often dim once they are benched, it would be a move of last resort.

However, there would be two scenarios where it could make sense for Buffalo to start Anderson. The first would be if the Bills are able to win enough games over the coming weeks that Allen's deficiencies as a rookie starter would be holding the team back from a playoff berth. If McDermott felt he owed it to his locker room to go as far as possible this season, Anderson could offer a steadier presence at quarterback than Allen.

The second situation would be if the wheels fall off so badly on the Bills' season that continuing Allen would do more harm than benefit to his development. That could be the result of a trade of key pieces around Allen on offense (e.g., LeSean McCoy) or further problems along the offensive line. In either case, Anderson could get the Bills mercifully to the finish line before they restocked their offense around Allen for 2019.

Right now, it seems unlikely Anderson will start for the Bills, but the possibility cannot be ruled out.

"Don’t get me wrong," Anderson said Wednesday. "I’m still a competitor. I’m going to push [Allen and Peterman] once my old body starts feeling right. I’m going to go out and practice like I always have."