MONTREAL -- Substitute Peter Byers scored in injury time to lift the Montreal Impact to a 1-0 victory over Vancouver that prevented the Whitecaps from clinching a USL-1 playoff spot on Wednesday night at Saputo Stadium.

Byers, who had a goal called back by a quick whistle in the 81st minute, fought off three defenders inside the penalty area before slipping a left-footed inside the far post.

Only 19 minutes earlier, the crowd of 11,867 booed when Byers' goal was called back because referee Silviu Petrescu had whistled for a Montreal free kick just before the Impact striker fought off a hold by Chris Pozniak and shot inside the far post from 12 yards.

They booed again as Montreal sweeper Nevio Pizzolitto was shown the yellow card -- which will bring a two-game suspension for accumulated cautions -- in the 83rd, and again when Byers was hauled down by goalkeeper Jay Nolly to nullify a chance in the 86th.

Montreal (12-10-6) clinched a berth in the playoffs when Rochester beat eighth-place Miami FC on Tuesday night, but the Whitecaps needed one point to be assured of playing in the post-season. The top seven teams make the playoffs.

Vancouver should get the point it needs as it ends the season at home against USL-1's two weakest clubs -- Sunday against Austin and Sept. 18 against Cleveland.

There was no playing for a draw as both clubs came out attacking, and the Impact had the lion's share of chances in a scoreless first half.

Only three minutes in, Eduardo Sebrango was stopped at point blank by Jay Nolly and Tony Donatelli put the rebound over the bar. Leonardo DiLorenzo had a glittering chance from the left side in the 13th minute but shot wide, while Roberto Brown was on the doorstep in the 27th but his shot went off Nolly's leg.

Sebrango left the match at half-time due to a fractured right hand and was replaced by Byers.

The Whitecaps had the best chances early in the second half, as Charles Gbeke's bullet drive from 25 yards was stopped in the 65th minute and Tyrel Burgess forced a quick save in the 72nd.

It had the makings of a grudge match.

On June 18, the Whitecaps arrived two days early hoping to collect the trophy for the Nutrilite Canadian Championship, only to see the Impact dress a weak side and crumble 6-1 before Toronto FC, denying Vancouver a spot in the CONCACAF Champions League. Two days later, Montreal beat the Whitecaps in a regular-season game.

The Whitecaps were without veteran midfielder Martin Nash, who missed a third game with a hamstring injury, but striker Marlon James returned from missing three weeks with a groin problem and got into the game in the 78th minute.

Montreal goalkeeper Matt Jordan was out with a hand injury, so ex-Whitecap Srdjan Djekanovic started.