Neiswander will be going for three wins in a row when the Alouettes (6-8) take on the Winnipeg Blue Bombers (2-12) on Monday afternoon. He seems to be building chemistry with his receivers and offensive line.
But it may only last until Calvillo returns from the concussion he suffered on Aug. 17 against Saskatchewan. So far, the target date for the CFL's all-time passing leader to return is Nov. 1, when the Alouettes visit Toronto for their final game of the regular season. Just in time for the playoffs.
Despite his success of late, Neiswander says he will gladly hand the ball back to his 41-year-old mentor.
"I'm the guy through the rest of this week and after that, we'll get ready for next week," Neiswander said Friday. "But if and when A.C. comes back, A.C.'s the man.
"And there won't be any doubt who is in there. I fully support him. Being the all-time leading passer in CFL history, I have way too much respect for him — and so does everyone else on our team — to even consider anything else. That's just the way it is."
Calvillo turned up at practice this week to say he is progressing in his recovery and has resumed attending meetings. He is expected back on the field next week, but only to begin reintegrating with the team and not to take any snaps or throw any passes.
Due to the unpredictability of concussions, there is no guarantee he will be able to play again this season, which could spell the end of a 20-year CFL career in which he won three Grey Cups and set records for passing yards, completions and touchdown passes.
If not, Neiswander has seized the starting job and will be in position to take over for keeps next season, although he will have competition from rookie Tanner Marsh and 2007 Heismann Trophy winner Troy Smith.
Marsh looked to have taken the job from Neiswander when he put his own two-game streak together in mid-season, but the 23-year-old was already struggling when he injured a thumb during a Sept. 15 loss in Vancouver.
Marsh resumed practising, and was throwing the ball fairly well this week. He may be able to suit up against Winnipeg as the third-string pivot.
Smith only joined the team in August. He has got into games for a play or two to hand off or run the ball himself, but mostly he was brought into learn the offence and be ready for 2014.
Montreal also acquired former Bombers quarterback Alex Brink this week, mainly as experienced insurance at that position.
Neiswander has not put up the spectacular numbers Calvillo was known for, but he has been getting the job done. He has started the last three games and has completed a modest 62 passes for 809 yards, but seven were for TDs and only one was intercepted.
"As a quarterback, any time you can gain experience it allows you to have a higher comfort level," said the Winnsboro, Texas, native, who is in his third season in Montreal. "It's one thing to watch and study and get reps in practice and it's another thing to get to go out there and execute on offence live, in a game.
"The chemistry gets better and better the more reps you get."
Coach and general manager Jim Popp said the team is over the shock of losing Calvillo for an extended period and has learned to have confidence that it can win with either Neiswander or Marsh behind centre.
He said the trick with Neiswander was to tweak the offence to suit his style and abilities.
"It starts with the coaches," said Popp. "We have to try to put him in a situation not to turn the ball over and not to feel that they have to throw for 300 or 400 yards.
"We just want them to manage the game — play safe, go where your reads take you. And then the offence will execute. We've done a better job of that in the last few weeks."
Neiswander has also had help from his receivers — and not just rookie Duron Carter's spectacular catches or S.J. Green's dependable hands.
"I feel the confidence level is going up for him," said veteran receiver Arland Bruce. "That's from us running backs and receivers encouraging him, saying 'this is great, this is what we like.'
"That raises his confidence and it raises our play too when you have that communication right on point. Josh is doing a great job of communicating, talking to us, and we're letting him know what we see."
"He's starting to become more comfortable in this offence, which is making everyone around him more comfortable," said Green. "Once that happens and guys start to settle in, things progressively look a little better on game day."
The Alouettes can clinch a playoff spot with a win. The team has not missed the post-season since it returned to Montreal in 1996, but things looked dicey earlier in the campaign.
They still have a long-shot chance to overtake Toronto (9-5) for first place in the East, and a clear chance to edge Hamilton (7-7) out of second place. After the Bombers, the Alouettes play back-to-back games against the Tiger-Cats.