MONTREAL — Every team is filled with optimism at the start of a season, even the underdog Montreal Impact.

So even if new coach Remi Garde has admitted his roster is a little thin after an off-season of sweeping player changes, six weeks of training and a 3-1-1 pre-season record have the Impact feeling positive heading into their Major League Soccer regular-season opener Sunday against the Whitecaps in Vancouver.

"With a new coaching staff, new players, it felt like we started from zero," midfielder Samuel Piette said Tuesday. "But the team has to be ready because the championship starts Sunday and it doesn't stop.

"I'm confident with the players and staff we have."

The Impact cleaned house after a disappointing 11-17-6 campaign, firing coach Mauro Biello a year after he led them to the Eastern Conference final. The club brought in former Lyon boss Garde from France with a mandate to make the squad fitter, younger and better able to defend.

Players say they are certainly better conditioned this season and like what they've seen from a tighter defensive system so far. They are also younger, thanks partly to the retirement of veterans Patrice Bernier and Hassoun Camara and trading of central defender Laurent Ciman to expansion Los Angeles FC.

They also lost play-making midfielder Blerim Dzemaili to Bologna FC, but got back a solid No. 8 in Saphir Taider from the Italian club that is co-owned by Impact president Joey Saputo. Left back Ambroise Oyongo took his speed and flair to Montpellier in the French league and gifted teenager Ballou Tabla left for Spanish giant Barcelona.

A raft of new players came in, including Canadian right back Michael Petrasso, former Toronto FC right-side attacker Raheem Edwards and 20-year-old Chilean attacking midfielder Jeisson Vargas.

"The parity in this league from year to year is crazy," said goalkeeper Evan Bush. "You saw last year, Chicago was picked at the bottom and they rose up.

"Every year there are teams that rise to the occasion and there's no reason we can't."

But depth is an issue, particularly with striker Anthony Jackson-Hamel (torn hamstring) and central defender Kyle Fisher (fractured shin) injured.

And there was concern Tuesday when new centreback Zakaria Diallo had to be helped off the field during training after a fall. A team spokesman said there was no confirmation yet on what injury Diallo suffered or how long he would be out of action. A report from TVA Sport called it a ruptured Achilles tendon that would keep him out for months.

Diallo had taken Ciman's spot as the anchor of the back line. The only other healthy centrebacks are Victor Cabrera and 20-year-old Thomas Meilleur-Giguere, although new fullback Jukka Raitala can play in the middle.

It muddies the picture of a possible starting 11, which would have Bush in goal with Petrasso or returnee Chris Duvall at right fullback and either Daniel Lovitz or Raitala on the left. Piette and Taider may be the holding midfielders, with scoring star Ignacio Piatti on the left side, Edwards on right wing, Vargas in the middle and veteran Matteo Mancosu up front.

Returning midfielder Marco Donadel and forward Michael Salazar are also in the picture.

Garde said he has an idea of what the starting lineup will look like but may change his mind by Sunday.

He acknowledged he didn't land all the players he targeted in the off-season but still expects to field a winning team. He will try to add more talent in the summer transfer window.

The start of the season promises to be especially difficult. Not only are players building chemistry, six of the club's first eight games are on the road where it is particularly difficult to win in MLS.

"It's the start of a long season so the game's very important," he said. "Not only because it's the opening game but it lets us see where we are against an (MLS) opponent, even if we got a glimpse of it in the pre-season against Chicago, Philadelphia or New York (City)."

Garde said the team won't name a captain to replace Bernier, but would share the armband among a few players.

He also hopes the Impact will sign midfielder Ken Krolicki, the only player it selected in the MLS draft; in the third round. Montreal traded its two first-round picks for $350,000 in allocation money.