Of the five team captains who led the Buffalo Bills to their first playoff berth since 1999, three might not be with the team in 2018.

Center Eric Wood, one of those captains, announced his retirement Friday because of a neck injury discovered by team doctors in a postseason physical. The injury will prevent him from being cleared to play.

Two other captains, quarterback Tyrod Taylor and defensive tackle Kyle Williams, might not return next season. Taylor is under contract but could be released as the Bills look to upgrade from an offense that scored only three points in a wild-card playoff loss to Jacksonville. Williams, who turns 35 in June, said after the defeat that he will take time to ponder his playing future. Williams will become an unrestricted free agent in March.

That leaves linebacker Lorenzo Alexander, who turns 35 in May, and kicker Stephen Hauschka as the only two captains likely to remain with Buffalo in 2018. Alexander will become a free agent after next season.

The Bills put the pieces together this past season to finish with a surprising 9-7 record and sneak into the playoffs with a fourth-and-12 touchdown by the Cincinnati Bengals in a regular-season finale win over the Baltimore Ravens. Leadership in the locker room from Wood and Williams was part of what kept the Bills' ship steady even after a three-game losing streak in November.

Now Wood is gone and other veterans in the locker room might follow, by their choice or the team's. Including Williams, the Bills have 18 unrestricted free agents who will be free to sign with other teams March 14. Starting cornerback E.J. Gaines and starting middle linebacker Preston Brown headline that group.

After the Bills turned over about half of their roster between 2016 and 2017, extensive turnover is possible again this offseason. Wood's departure adds an unexpected wrinkle -- and creates a leadership void in the locker room and in the community.

Coach Sean McDermott spoke last season about the need to develop a "second crust" of leaders behind the team captains, and that becomes more important with Wood's retirement. Sixth-year safeties Micah Hyde and Jordan Poyer will be the two players McDermott could target to lead the locker room in 2018. Both emerged as stronger voices last season and were among the best in the NFL at their position, with Hyde making the Pro Bowl.

Replacing Wood on the field could be Ryan Groy. A versatile reserve offensive lineman who has played guard, center and blocking tight end, Groy started the final seven games of the 2016 season when Wood fractured his leg. He performed well enough for the Bills to match the Los Angeles Rams' two-year, $5 million offer sheet when Groy was a restricted free agent last offseason.

Groy is 27, so, although this is not something the Bills planned or preferred, he would offer more youth than Wood, who turns 32 in March. General manager Brandon Beane has stressed the need to get younger in 2018 after having players 30 or older this past season play the fifth-most snaps in the NFL.

Wood's retirement means the Bills must still swallow a large chunk of the two-year contract extension (through 2019) he signed this past August. NFL salary-cap rules stipulate that retiring players be treated the same as players being released.

Wood has a $4.8 million base salary in 2018 that is guaranteed for injury. If the Bills release him or he is placed on the reserve/retired list before June 1, Wood will count $10.39 million against the Bills' salary cap in 2018 -- more than his $8.625 million hit had he remained playing.

If the Bills release Wood after June 1 or he officially retires after that date, the Bills would take a $8.225 million cap hit in 2018 and would have $2.166 million from Wood's contract count in 2019.