REGINA — Mystery surrounds who will start at quarterback for Saskatchewan on Sunday in the West Division semifinal despite a short-lived tweet on the Roughriders' social media account that said otherwise.

The team announced on Twitter Saturday that Zach Collaros would make his 15th start of the season against the Winnipeg Blue Bombers after speculation surrounded his health all week. The tweet was deleted hours later and a story on the Riders' website clarified Collaros could start.

Collaros himself wouldn't say if he or Canadian Brandon Bridge would get the start. He wouldn't even say if he would dress.

"I can't say anything, no," Collaros told reporters Saturday.

Collaros was hurt in the Riders' regular season finale on Oct. 27 against B.C. after taking a hit late in the first quarter from Odell Willis.

Collaros passed concussion test protocol and practised all week. The team's QB depth chart lists Collaros at the top followed by Bridge, David Watford and new signing Drew Tate. Only three quarterbacks can dress in the game.

"We prepare both quarterbacks to play and that's it," head coach Chris Jones said.

"You have to have them both ready because if one of them can't play, and quite honestly you're a play away from that happening every single week, you better have two prepared."

Saskatchewan was without Collaros for four games earlier this season after he suffered a concussion in Week 2. The team went 2-2 in his absence.

Collaros has thrown for 2,999 yards, nine touchdowns and 13 interceptions in 14 games this year. Bridge, a Toronto native, appeared in eight games for the Riders and threw for 804 yards, one touchdown and three interceptions.

Collaros said he feels fine and is excited at the prospect of playing in Saskatchewan's first home playoff game since the 2013 Grey Cup.

"This is why you play the game to play in big moments like this," he said.

Winnipeg head coach Mike O'Shea said he doesn't think Jones is confused about his quarterback situation and knows exactly what he's doing.

"I'm sure if he's got the opportunity to use both (quarterbacks), he'll use both," O'Shea said. "We're prepared for that."

Roughriders centre Brendon LaBatte said it doesn't make a difference who's starting as he's given snaps to both players several times this year.

"At least from what we hear in the huddle, there's no difference between the two," LaBatte said. "It's a little bit different tone of voice, but that's really where it ends."

The winner of Sunday's game will play the Calgary Stampeders in the West final next Sunday.

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WINNIPEG BLUE BOMBERS (10-8) at SASKATCHEWAN ROUGHRIDERS (12-6)

Sunday, West Division semifinal, Mosaic Stadium

PLAYOFF HISTORY — The Riders are hosting Winnipeg in a playoff game for the first time since 1975. The last time the Blue Bombers beat Saskatchewan in the playoffs was the 1965 West Division semifinal. Mosaic Stadium, which opened in 2017, will host its first playoff game. The 2007 Grey Cup in Toronto was the last time the two teams faced off in the post-season.

HEAD TO HEAD — Saskatchewan went 2-1 in the regular season against the Blue Bombers. Winnipeg shut out the Riders 31-0 in the last meeting on Oct. 13 and intercepted Collaros twice. Adam Bighill had a massive game for the Bombers in that matchup, collecting eight tackles, three sacks and a forced fumble.

HARRIS THE KEY — Jones said if Winnipeg runs the ball well, they will be tough to stop. Blue Bombers running back Andrew Harris captured his second rushing title this season with 1,390 rushing yards and eight touchdowns. None of those TDs have come against the Riders.

IT'S CHILLY — Weather could play a factor on Sunday with temperatures forecasted to reach -22 C with the wind chill in the afternoon. There's also a chance of flurries.

— Follow @RyanBMcKenna on Twitter