But things can change quickly in sports.
Suddenly, with injuries and personnel changes, the Scottish-born Mallace has become a regular defensive midfielder with the Major League Soccer club through the final weeks of a rough season for the 6-18-6 Impact.
And he is staking a claim for regular work next year as well.
"There are some injuries now and that's obviously going in my favour," the 24-year-old said Wednesday. "I'm trying to take advantage of that."
After starting only two games through the first five months, Mallace has now been in the first 11 in six matches in a row, and seven of the last eight. He has appeared in nine straight games.
An imposing figure at six-foot-three, he has brought an energetic, physical game to the defensive midfielder position. And he scored his first MLS goal along the way at New England.
It helped that designated player Hernan Bernardello joined Mexican club Cruz Azul in mid-season, and that Colin Warner was traded to Toronto FC.
When team captain Patrice Bernier returned with an injury from a stint with Canada's national team in August, it left a void at the back of midfield that Mallace was eager to fill.
"He's got opportunities and that's what it's all about," said coach Frank Klopas. "Sometimes injuries occur and players get chances to play and he's taking advantage of that.
"He's done well. He can always improve at times making better decisions with the ball, but he's had some very good games in the middle for us."
For the first time since he was drafted in the second round, 20th overall, by Montreal in 2012, Mallace looks like he has found his niche.
He was used sparingly at fullback as a rookie under coach Jesse Marsch in Montreal's MLS expansion year. And when it didn't get any better under Marco Schallibaum last season, he was loaned out Minnesota United of the NASL for the rest of the campaign.
With former Chicago Fire boss Klopas in charge this season, Mallace turned up at training camp determined to earn a spot in the midfield. It took most of the season, but he's finally getting his shot.
"Over the last few games I've been getting my confidence up," said Mallace. "I'm showing that I'm a player in this league that can play game in, game out, and can play with confidence in the middle of the field.
"I can keep the ball for the team, win tackles, distribute the ball and get forward and maybe get some assists and score some goals."
With three head coaches in as many seasons, there have been wild shifts in the fortunes of several players, who are favoured by one coach only to be shunned by the next or vice versa.
Mallace described his path as "steady but upwards.
"It's been a long run," he siad. "When you're young and you're not playing in this league, it's difficult. I made that decision last year to go on loan and I think it helped me on and off the field, and helped me grow as a player.
"This year, I've got the most minutes of my career and I think I'm making the most of it."
Mallace was born in Torphichen in West Lothian, Scotland, and his family moved to Mendota Heights, Minn., when he was nine. Only a trace of a Scottish accent remains.
He made his mark in soccer at Marquette University, where he was Big East midfielder of the year in 2011.
When Montreal participated it its first MLS SuperDraft in 2012, all the attention went to first overall pick Andrew Wenger, a big, fast forward from Duke University who never quite found his groove and was traded this season to Philadelphia for striker Jack McInerney.
Now Mallace has to keep the niche he has carved for himself through the inevitable personnel changes that will come this winter. Also, Bernier is due back from his injury soon, and Klopas will have to decide whether to use them as a twosome at the back of midfield or relegate one of them to the bench.
Either way, Mallace has had a string of consecutive games to show what he can do.
"I want to be a player every week," said Mallace. " Not 'will he be in the squad?' I want it to be: 'That's our guy in the middle for next year.'"