09/23/2014 02:14 EDT | Updated 11/23/2014 05:59 EST

Calgary's Cornish returns for game against Lions, but not QB Bo Levi Mitchell

CALGARY - With their momentum suddenly halted, the Calgary Stampeders are collecting themselves for what will be a tough fight for the West Division over the final third of the regular season.

At 10-2, Calgary still tops the CFL and West Division standings. But a 31-15 loss Sunday to the Alouettes in Montreal was a dash of cold water in the face of league's top team.

A week earlier, Calgary had to overcome a 19-point deficit at halftime to beat the Toronto Argonauts.

The Stampeders have six games remaining against three division opponents, starting Saturday at home against the B.C. Lions (7-5). The Lions downed the host Stamps 25-24 on Aug. 1 for Calgary's only other loss this season.

The Stampeders twice face the Saskatchewan Roughriders (9-3) and Winnipeg Blue Bombers (6-6) before the season finale against the Lions.

Calgary is two points up on the Roughriders, four on the Edmonton Eskimos and six on the Lions. The Stampeders swept the season series against the Eskimos.

This home stretch will determine who gets what in terms of a playoff berth, home playoff games and the bye to the West Division final.

"This is the best part of the season," running back Jon Cornish said. "Over the last few years, I've sort of realized that nothing really matters except for these last six games.

"With that in mind, I think this team is really going to prepare for that. We're going to be ready to take on all these opponents because we're playing great teams."

Cornish, the CFL's most outstanding player in 2013 and leading rusher the last two seasons, will play Saturday after sitting out the game in Montreal.

Cornish didn't travel with the team in order to heal undisclosed aches and pains. The 29-year-old from New Westminster, B.C., missed six games in July and August with concussion symptoms.

"I don't think I'll have to miss any more games," Cornish said. "That's why I took this time, so I would be ready. These teams are going to be ready to play us, so I want to be ready for them."

Quarterback Bo Levi Mitchell isn't ready to return, which means Drew Tate gets his second straight start of the season. Mitchell sprained his ankle and stretched a ligament in his left leg late in the game versus the Argos.

Tate took first-team reps Tuesday, while Mitchell practised lightly wearing a brace on his left leg.

"He's progressing at a good tempo," Stampeder coach John Hufnagel said of Mitchell. "Probably will not make this game, maybe as a No. 3 guy. Hopefully he'll be full-go for the next game."

Calgary has built a reputation for winning despite injuries. They were 14-4 last season despite using three different starting quarterbacks.

But the Stampeders may have neared the limit of their depth Sunday in Montreal.

Not only were the starting quarterback and star running back absent, but leading receiver Marquay McDaniel was on the six-game injured list with a broken bone in his hand from the Toronto game.

The Stampeders managed two touchdowns on the ground and less than 300 yards on offence, but it was on the other side of the ball where Calgary was uncharacteristically porous.

A team allowing an average of 18 points per game gave up 31. Montreal's offence had the ball for almost 38 minutes, while Calgary's time of possession was just over 23.

Team sack leader Charleston Hughes (foot), defensive tackle Demonte Bolden (leg) and Hughes's backup Ben D'Aguilar (knee) were also injured in the Toronto game.

That trio didn't play in Montreal and they won't Saturday against the Lions. Bolden is on the six-game injured list. It's further decimated a defensive line that was already without starters Micah Johnson (knee) and Corey Mace (foot).

"That's no excuse for the way we played," defensive end Shawn Lemon said. "It doesn't matter who is out. If you're on this team we believe we can step up. I take it upon myself as well. I didn't play up to my expectations and I wasn't an impact in the last game.

"Just got to gain momentum back. We took a step back last week so just come out and get back to what we were doing the first 11 weeks of the season."

The Stampeders added defensive lineman Caesar Rayford to the practice roster Tuesday. He played seven games and recorded five tackles for the NFL's Dallas Cowboys last season. The six-foot-seven University of Washington product also spent time on the Lions practice roster in 2008.