Allen won't be eligible to return from injury until late October. ((Adrian Wyld/Canadian Press))

Toronto Argonauts quarterback Damon Allen has been placed on the long-term injured list on Thursday, putting the veteran's CFL future in doubt.

Allen, who ruptured tendons in his toe in a game Aug. 2 against Montreal, won't be eligible to return for nine games, or until Week 17 of the season, the third week of October.

The Argos (2-4) have endured a rash of injuries at the position, with four separate players taking snaps under centre in just six games.

Michael Bishop, who seemed on his way to taking over the No. 1 quarterback job, is still a few weeks away from returning from a wristfracture suffered against Calgary on July 12.

Former NFL quarterback Mike McMahon was ineffective in limited duty for the Argos, who turned to Rocky Butler after Allen's injury.

Former Heisman Trophy winner Eric Crouch was placed on the nine-game injured list prior to the start of the season.

Allen, 44, re-signed for one more year to try and help the Argos reach the Grey Cup, to be played in Toronto in November. The 22-year CFL veteran and four-time Grey Cup winner is pro football's all-time leader in passing yards.

Butler will start for Toronto against his former team, the Saskatchewan Roughriders, on Friday.