Didier Deschamps discovered the difficulty of fighting for trophies on two fronts when his three first-choice strikers suffered injuries in domestic action to leave the Marseille manager with a major selection problem ahead of Wednesday's visit of Manchester United in the last 16 of the Champions League.

Having been shunted down to fourth place in Ligue 1 because of Lyon's emphatic victory over Nancy on Friday night Deschamps felt he had no choice but to field a strong side at home to St‑Etienne and although their 2-1 victory sent them back into second place in the table it came at a heavy cost, as André‑Pierre Gignac, Brandão and Loïc Rémy all failed to finish the match.

Marseille already knew they would have to take on Sir Alex Ferguson's men without the injured France international forward Mathieu Valbuena. Rémy is said to have a good chance of recovering from his ankle knock in time to take on United but the fitness of Brandão, who also damaged his ankle, remains uncertain while Gignac, the club's most in-form player this year, will definitely miss the match, a slight tear of a quadriceps will rule him out for up to two weeks. Tests on Sunday will confirm the extent of the injury and whether the forward will be able to face United in the return leg.

Marseille paid €18m (£14.7m) to sign Gignac from Toulouse last summer and he initially struggled to prove his worth – some of his displays earlier this season were so poor that he was booed off the pitch by Marseille's always-vociferous ultras. However for last month's League Cup tie against Toulouse Deschamps relieved the 25-year-old of the burden of being the team's attacking fulcrum and instead stationed him wide on the left – and that turned out to be a masterstroke as the player exploited the increased space given to strike five goals in five games, including a spectacular double in last week's win over Sochaux. His transformation was such that he was billed as the man most likely to torment United's defence. Instead Deschamps now finds himself wondering whether he will have enough fit forwards to deploy his usual 4-3-3 formation and may have to ponder a tactical rejig.

The only positive note to emerge from last night's game – beyond the three points – was the fine performance of Lucho González. The Argentinian playmaker was the inspiration behind Marseille's league title last season – their first in 18 years – but his form had dipped alarmingly in recent months, the nadir coming three weeks ago at Monaco when he was substituted in the 79th minute having barely touched the ball.

Against Sochaux last weekend Deschamps tinkered with his tactics in a bid to revitalise the Argentinian, fielding two holding midfielders, Charles Kaboré and the former West Ham United player Edouard Cissé, to liberate González from all defensive duties and allow him to concentrate on creating.

The ploy worked as González produced his best performance of the year. Last night he continued his improvement and scored Marseille's opening goal in the 67th minute. Eleven minutes later his corner lead to Marseille's second, which Rémy swept into the net. Three minutes from time Rémy was caught by a late tackle by Blaise Matuidi and hobbled off the pitch. Christophe Landrin pulled a goal back for the visitors in the last minute but Marseille held on. Their chances of winning against United, however, were left seriously harmed.