The spell has broken for Louis van Gaal at Manchester United

LOUIS VAN GAAL arrived at Old Trafford last summer having embellished a glittering CV by guiding an unfancied Holland team to third place in the World Cup.

Louis van Gaal van Gaal has a testing month aheadGETTY

Louis van Gaal van Gaal has a testing month ahead

Now he has 10 games to prove that he has not lost the managerial magic that convinced Manchester United he was the man to turn round their fortunes.

Monday's FA Cup exit to Arsenal means that for the first time since the late 1980s United will have gone two seasons without winning any silverware.

And Van Gaal has to ensure that the psychological fall-out from the defeat does not impair what has always been his main task this season - ensuring the club finish in the top four and return to the Champions League next season.

He faces a definining month in his first campaign as manager, with Tottenham, Liverpool, Manchester City and Chelsea providing four of their next five matches.

Failure to stay in the top four will not only be another major dent to United's pride and prestige but also their revenue.

This season's absence from Europe's top table has cost them about £50million and, if they fail again, it will also lead to a reduction in the £750m kit deal with adidas that launches next summer.

It could also hinder attempts to attract top-quality players to Old Trafford while possibly influencing the decision of goalkeeper David De Gea whether to ignore overtures from Real Madrid and commit his future to United.

Former skipper Roy Keane believes it will be "disaster" if United miss out on the Champions League for a second successive season but believes Van Gaal should be given the time that English football's most successful club did not afford his predecessor David Moyes.

The inside word at Old Trafford is that United's faith in Van Gaal will remain unshaken, even if he misses out on the top four.

Unlike Moyes a year ago when defeats by Olympiakos, Liverpool, Manchester City and Everton convinced the hierarchy a change had to be made, the belief is that progress is being made under the demanding Dutchman, even if many supporters and pundits are not seeing it.

And the clubs owners, the Glazers, are understood to be ready to back him to complete his squad overhaul with another £150m-plus transfer war chest this summer when United are likely to pursue targets like Nathaniel Clyne, Mats Hummels, Kevin Strootman, Memphis Depay, Saido Berahinho and free agent Danny Ings, who apparently impressed Van Gaal in Burnley's defeat at Old Trafford last month.

Memphis Depay Player Profile

The fervent hope is that any newcomers will have a more immediate impact than last summer's arrivals, Angel Di Maria, Radamel Falcao, Daley Blind, Marcos Rojo, Luke Shaw and Ander Herrera.

Falcao's loan spell from Monaco will not become a permanent move while Juan Mata, left on the bench in recent matches, appears surplus to Van Gaal's plans.

No one felt the cup exit more than Wayne Rooney - his 13th season of heartbreak in the one competition he has failed to win - but the Untied captain admits they cannot allow it to have an adverse effect on their remaining League matches.

"We're gutted because we knew we would have had a great opportunity to go on and win the Cup," he said.

"It's a hard one to take but we have to lift ourselves now for the games ahead. We've got a tough few games coming up, starting against Tottenham on Sunday so we have to move on from this. It's difficult at times - but we have to make sure we are right on Sunday."

Would you like to receive news notifications from Daily Express?