Sir Alex Ferguson has warned his Manchester United stars that it won't be easy to kill off Marseille in the Champions League last 16 second leg on Tuesday.
Ferguson's side got their spluttering season back on track with a 2-0 win over Arsenal in the FA Cup quarter-finals on Saturday, but the Gunners created enough chances to suggest all is not completely well with United just yet.
There is no margin for error at Old Trafford on Tuesday as the Premier League leaders will be eliminated from Europe's elite club competition if Marseille can secure a score draw, following the goalless first leg in the south of France.
Ferguson knows Didier Deschamps' team possess a sharp enough attack to pierce United's occasionally careless defence and snatch a priceless away goal.
United crashed against Bayern Munich on away goals in the last eight last season and Ferguson, fearing a repeat, was sufficiently concerned to fly to France on Friday to watch Marseille's 2-0 win at Rennes.
He returned to tell his players not to under-estimate the size of the task facing them.
"The first leg was a terrible game, a shocking match," he said. "It will be a better game on Tuesday.
"Marseille will be planning on how they're going to score a goal and I think they'll try to start the game very quickly -- that's a certainty - and we have to be prepared for that.
"It will be important to defend well. All the big games will be that way for us now."
Reports on Sunday that Ferguson will consider selling Wayne Rooney in the close-season as a result of his strained relationship with the striker will quickly be forgotten if he reproduces the kind of dynamic display that helped vanquish Arsenal.
Rooney came close to quitting Old Trafford after handing in a transfer request earlier this season before eventually signing a new contract.
His form since then has fluctuated dramatically, with occasional highs marred by too many lacklustre performances.
But, used in a variety of roles against Arsenal, Rooney showed why he remains so valuable to United and Ferguson said: "He did a great job for us. Centre midfield in the first half, second half he could have scored maybe a hat-trick really.
"He took his goal well, he's continued his great record against Arsenal, scoring-wise. I think Wayne, and all the rest, earned their corn."
With Rio Ferdinand, Darren Fletcher and Michael Carrick all injured, Ferguson will keep faith with young defender Chris Smalling and recall Paul Scholes and Ryan Giggs after resting the veteran midfielders on Saturday.
Ecuador winger Antonio Valencia, back after six months out with a broken leg, could also feature and Nani may make a surprise return following his recent injury against Liverpool.
The slightly uncertain nature of Ferguson's selection should encourage Marseille to believe they can claim a famous scalp.
Under Deschamps' astute leadership, Marseille finally lived up to their billing as France's biggest club by winning their first league title in 18 years last season.
Deschamps certainly has the pedigree to worry United - in 23 European Cup and Champions League meetings with British clubs as a player and coach, the Frenchman has tasted defeat just five times.
However, Marseille's chances will be dented by the absence of Brazilian striker Brandao, who incurred Deschamps' wrath after he was placed under formal police investigation on suspicion of a sexual assault.
Brandao is on bail and will not travel to Manchester after being left out of the Rennes match.
Instead Deschamps will need an influential display from playmaker Mathieu Valbuena, who recently returned after four weeks out with a knee injury.
"Many people said we would collapse, but we're still here, with our qualities and our flaws," Deschamps said.