REGINA -- The Montreal Alouettes lost the game and potentially something much bigger.
Alouettes quarterback Anthony Calvillo left Saturday's 24-21 loss to the Roughriders with a suspected concussion after taking a hit from Saskatchewan defensive end Ricky Foley on the first play of the second quarter and did not return.
"I've got a headache, I felt it right when I got hit and from there it hasn't gone away so they just kept me away from the game," said Calvillo, who added that he didn't remember being hit but didn't think the impact with the ground was what caused his injury.
"I'm assuming that it is (a concussion)."
Calvillo had not been formally diagnosed in the minutes immediately after the game and said his status for Montreal's game against the B.C. Lions on Thursday would be determined later in the week.
He was replaced in the game by Josh Neiswander, who completed 12 of 30 passes for 147 yards and two interceptions in his CFL debut at quarterback.
The win solidified the Roughriders (6-1) place atop the CFL's West Division while Montreal (2-5) lost its second straight game under new head coach Jim Popp, despite 146 yards receiving from S.J. Green.
It turned out Calvillo's injury was only a sign of things to come for both teams.
Montreal's injured list grew before halftime when receiver Brandon London took a helmet-to-helmet hit from Saskatchewan safety Tyron Brackenridge and did not return.
Alouettes linebacker Kyries Hebert was also knocked out of the game on the same drive. He was kneed in the head by teammate Martin Bedard while covering a punt.
The Roughriders weren't immune to the injury bug either.
Wide receiver Rob Bagg went down just before halftime, appearing to injure his left knee on a routine blocking assignment. Bagg had season-ending surgery in 2012 to repair a torn ACL in the same knee.
"I feel so bad for the guy," said Riders slotback Geroy Simon, who became the third player in CFL history to reach 1,000 receptions when he caught a four-yard pass from Darian Durant early in the fourth quarter.
"I'm a fan of Rob Bagg, even when I played for B.C. all those years. He plays so hard and he's such a gifted, talented guy. To see him go down, no matter what it is, you don't want to see a guy like that get hurt because he works so hard in practice and puts everything he has into it."
Roughriders head coach Corey Chamblin had no update on Bagg's condition after the game.
Saskatchewan survived another scare earlier in the game when Weston Dressler came up unable to move his left shoulder after diving out the back of the end zone for a 22-yard touchdown catch in the first quarter.
Unlike the others, Dressler was able to return to the game.
That twist of fate proved critical late in the game when Dressler returned a Montreal punt 38 yards to the Alouettes' 38-yard line.
Dressler's punt return put the Riders in scoring position and Chris Milo won the game on a 36-yard field goal with no time left on the clock.
Dressler was filling in for Jock Sanders after Sanders fumbled twice deep in Saskatchewan territory, setting up two of Alouettes kicker Sean Whyte's four field goals on the night.
"It didn't happen the way we planned it but we kept fighting, (Durant) trusted me and I made a play when it came to me," said Taj Smith, who caught a 60-yard touchdown pass from Durant to tie the game 21-21 with barely a minute to play.
That catch came just seconds after Jerald Brown returned Durant's second fumble of the game for a 54-yard score to put Montreal ahead by seven.
It was also finally enough to silence the boos of the third-largest crowd ever at Mosaic Stadium -- announced at 40,637. The fans showed their dissatisfaction with Durant through most of the third quarter.
Durant ultimately went 18-for-32 for 250 yards in his sixth straight game without an interception.
"The fans, they want perfection and I've been here eight years and I've been booed plenty of times so it was nothing new," he said.
"Of course it's nothing you want to hear but at the same time you understand why and if you don't want to hear it, just go out there and make plays and give them something to cheer about."
Saskatchewan led for most of the first half but had to rally for the win after Sanders coughed up the ball on the opening kickoff of the second half. That turnover gift-wrapped an 11-yard field goal from Whyte and gave the Alouettes an 11-9 lead.
The Riders tied the game when Whyte gave up a safety instead of punting from his own 11-yard line and took a temporary lead on the second play of the fourth quarter when Milo kicked a 26-yard field goal.
Milo has now hit all 16 of his field goal attempts this year.
Whyte tied the game 14-14 on his fourth field goal of the game early in the fourth quarter and had all of Montreal's offence up until that point, having also kicked two singles - one on his only missed field goal of the game and the other on a punt single in the third quarter.
Punter Ricky Schmitt also kicked two singles for Saskatchewan.