Calvillo, who is suspected of having a concussion, was among eight Alouettes injured in their 24-21 road loss to the Saskatchewan Roughriders on Saturday. And given Montreal's quick turnaround, interim head coach Popp is assuming all eight won't suit up against B.C. (5-2).
"Guys were getting MRIs, seeing doctors (Monday) and (Tuesday) they sit down and get the final word of where they are but we can't wait on that," the Alouettes' general manager said in a telephone interview. "We've had to move forward as though all eight aren't playing and if you get one or two back, then great.
"But we've had to go into the thinking mode that we're not going to have them and move forward."
Calvillo, who will celebrate his 41st birthday Friday, was injured in the first half after taking a hard hit from Saskatchewan defensive end Ricky Foley. Pro football's all-time passing leader had completed four-of-eight passes for 85 yards at the time with Montreal (2-5) trailing 7-3.
Backup Josh Neiswander replaced Calvillo, completing 12-of-30 passes for 147 yards and two interceptions. It was Neiswander's first CFL regular-season action since signing with Montreal in 2011.
"I've always said I don't want to know who our next quarterback is, I hope our starter stays on the field," Popp said. "That's a good sign.
"You find guys, you prep them and if they are called to play then they go out there and play and either you win with them or you don't and you realize if they've got it or they don't have it."
If Calvillo doesn't play against B.C., Popp would expect Neiswander to start but could also see rookie Tanner Marsh getting some playing time. Both took snaps with the starting offence in practice last week prior to Montreal's game in Regina.
"We planned last week that we'd play both if it came down to that and we ended up not because Josh handled it fairly well," Popp said. "He's the more experienced guy and he's looked good in practice but we could very easily see both of them if Anthony doesn't play."
Trouble is, Calvillo wasn't the only Alouette hurt in Regina. Also injured were linebackers Bryn Roy (knee), Jonathan Beaulieu-Richard (ankle) and Kyries Hebert (knee), long-snapper Martin Bedard (shoulder), tackle Josh Bourke (knee), safety Mike Edem (shoulder) and receiver Brandon London (head).
What's more, Roy, Beaulieu-Richard, Bedard, Bourke and Edem are all Canadians. Replacing all of them under normal circumstances would be a huge challenge, let alone on a short week.
"Even to get a guy off a practice roster, there's a process to it," Popp said. "If we were awarded a guy he wouldn't get here in time to practise so there's no sense in doing that.
"You get to what's on the street, well, we've made calls to the primary agents that represent most of the non-import guys and they don't have anybody . . . and the guys that were actually on the street a couple of weeks ago who are going back to CIS, well, they're in practice now and are going back to school so that's limited the number. But that's everybody's problem, not just ours."
Popp said London is definitely recovering from a concussion and won't play against the Lions. Earlier this month, Montreal lost veteran receiver Jamel Richardson, a two-time all-star, to a season-ending knee injury in practice.
Montreal wasn't the only CFL club hit hard by injuries last weekend.
Saskatchewan slotback Rob Bagg injured his left knee in the first half. The native of Kingston, Ont., had missed portions of the previous two seasons with injuries to both knees.
Bagg appeared to be in tears while walking off the field. An update on his status is expected Tuesday when the Riders return to practice.
Riders slotback Weston Dressler jammed his left shoulder against Montreal but remained in the game, finishing with five catches for 51 yards and a TD.
Calgary's Nik Lewis was among the many CFL players tweeting their best wishes to Bagg following his injury. Hours later, the Stampeders' veteran receiver suffered a fractured fibula in a 26-22 road loss to B.C. on Saturday night and is expected to miss six weeks.
Injuries and an early coaching change have combined to make for a difficult start to the 2013 season for Montreal. Popp is 0-2 as interim coach replacing Dan Hawkins, who was fired after just five games.
Presently Montreal has 12 players on the nine-game injured list and running backs Brandon Whitaker (separated shoulder) and Noel Devine (ankle sprain) both didn't play in Regina. Popp isn't optimistic either will suit up Thursday considering the Alouettes won't play again until Sept. 3 in Toronto and both could use the extra time to heal up.
"Listen, we've had that kind of year, we've had a lot of injuries," Popp said. "You don't always have that, you're very fortunate some years not to have as many injuries as others but I still believe we can win any game we go into.
"Yeah, we're missing very key people but we won't make that an excuse.''