But to Deslauriers, Marsh's pass was a work of art.
Sean Whyte kicked a 14-yard field goal on the final play of the game after Marsh threw a 57-yard pass to Deslauriers with 1.9 seconds remaining to give Montreal a come-from-behind 39-38 win over the B.C. Lions on Thursday night.
Marsh's last-gasp pass to Deslauriers at the seven-yard line set up the improbable comeback as the Alouettes overcame a 28-14 deficit before what remained of a crowd of 22,456 on a rainy night at Molson Stadium.
"I'll give him a jump ball every single time," said Marsh, who replaced Josh Neiswander to begin Montreal's fourth offensive series. "He's a great athlete and makes plays when he needs to."
Deslauriers said watching the pass coming in made him feel "like a photographer."
"It was such a pretty ball," Deslauriers said. "It was just up there forever."
Marsh threw for 329 yards despite completing only 14 of 32 pass attempts, including four interceptions.
"I showed that I was a rookie," said the 23-year-old Texan. "I made a lot of rookie mistakes that I have to fix to be a successful quarterback in this league, no doubt, and I've got to keep learning. It was a great team win but I did a lot of bad things and I've got to fix them."
Marsh, who was a senior at Arkansas Tech last season, also rushed for 71 yards on nine carries, including his first touchdown run in the third quarter after completing his first touchdown pass to S.J. Green in the second quarter.
Tyron Carrier returned a kick 90 yards to draw Montreal within 38-33 but the Alouettes failed to convert a two-point attempt.
Whyte had four field goals in the game.
The Alouettes (3-5) won for the first time in three games under general manager Jim Popp, who became Montreal's interim coach after he and owner Robert Wetenhall fired Dan Hawkins on Aug. 1.
Tim Brown returned a missed field goal 124 yards for a touchdown early in the third quarter and Travis Lulay threw a pair of touchdowns to Shawn Gore for B.C. (5-3), which had won two in a row.
"Going in up at halftime you've got to pull those victories off," Brown said.
Paul McCallum kicked five field goals for the Lions and Lulay threw his second touchdown pass to Gore, a 29-yard catch-and-run in the fourth quarter to put B.C. up 38-27.
McCallum, who kicked his fourth field goal at the end of the first half to put B.C. up 21-7, hit a 33-yarder 5:58 into the fourth. The veteran kicker also completed a 12-yard pass to Anton McKenzie for a first down on a fake punt in the second quarter.
Lulay threw a 10-yard touchdown pass to Gore in the first quarter.
"It's embarrassing," Gore said. "I think I can speak for most of the team when I say that it's a game that we didn't deserve to win. We didn't make the big plays needed when we had the opportunities. We had so many turnovers and didn't capitalize. Way too many field goals, not enough touchdowns, we left it all out there and we gave them that opportunity and we gave the game to them."
Neiswander got his first career start in place of Anthony Calvillo, who was knocked out of Saturday's 24-21 loss at Saskatchewan with a concussion.
Intercepted twice in the loss to the Roughriders, Neiswander was picked off by Ryan Phillips four plays into the Alouettes' opening drive.
He completed one three-yard pass to Deslauriers in three attempt before he was replaced by Marsh. He made his pro debut in the Alouettes' 38-13 loss to the Toronto Argonauts on Aug. 8.
"We didn't do a whole lot the first two or three series so we were like, 'Let's get Tanner in there like we said we would,' and then it seemed like he got hot," Popp said. "It worked. I'm very happy for him. The team rallied around him and they stuck together and it's just great for our organization."
Jerome Messam drew Montreal to 21-14 when he scored on a 16-yard run 38 seconds into the third after Carrier returned McCallum's second-half kickoff 65 yards.
Brown caught the ball deep in the end zone after a 53-yard field goal attempt by Whyte went wide left and ran the length of the field to put B.C. up 28-14 at 3:21 of the third. Brown scored on a 97-yard kick return in the Lions' 26-22 win over Calgary on Saturday.
Arland Bruce caught an 86-yard pass from Marsh 3:47 into the third. He caught seven passes for 167 yards, passing Brian Kelly to move into 10th place on the CFL's all-time receiving yards list.
"I'm speechless," Bruce said. "I'm glad to hear that, especially after a win. It's a humbling feeling to know about that. Thank you for telling me that because that's a rare achievement and I'm thankful."
Marsh completed the drive with a six-yard run at 5:24 as Montreal closed to within a touchdown.
"He knew how to move around the pocket, when to get out of the pocket when there was space to run, he did that effectively," Gore said. "That pocket-awareness I think is huge for a young quarterback. He didn't seem rattled by the defensive rush too much. He had a lot of composure."
Duron Carter, the son of Pro Football Hall of Famer Cris Carter, made his pro debut and caught a 52-yard pass from Marsh on Montreal's second-quarter scoring drive.
Green celebrated his touchdown by tossing the ball into the end zone stands before going back to successfully implore the fan who caught it to return it for the rookie quarterback.
"Tanner came to me and asked me for the ball back so the crowd was nice enough to throw that ball back to me," Green said. "I appreciate that."
After McCallum opened the scoring with a 45-yard field goal off the upright, B.C. made it a 5-0 lead 8:07 into the game when Whyte punted the ball out of the end zone to concede a safety after a replacement long snapper Patrick Lavoie sailed a snap way over his head.
Martin Bedard, Montreal's regular long snapper, is on the nine-game disabled list with a shoulder injury. He was among eight Alouettes who were injured in Saturday's loss.