5 Man United players that need to impress against Aston Villa…

If anything has been certain during Louis van Gaal's spell at Old Trafford, it's that his starting line ups are very much uncertain.

With the Dutchman seemingly yet to settle on his first XI, the following players really need to impress against Aston Villa on Friday. It's time for some members of the squad to start proving themselves... Sergio Romero The man who was signed merely as a precaution for David De Gea's move to Real Madrid has been immediately thrust into the spotlight. But after pulling off a string of saves to keep Spurs at bay last weekend, Romero has suddenly found himself a genuine contender to hold on to the No.1 spot. There has been talk of United bidding for Dutch keeper Jesper Cillessen should De Gea finally depart, but Romero can potentially quash those rumours with another impressive display at Villa. Luke Shaw Shaw struggled for fitness in his debut season at Old Trafford, with many questioning whether the youngster was aware of what it takes to succeed at a big club. However, having reportedly taken a fitness coach away with him for his summer break, he has returned looking a lot sharper. The jury is still out among some United supporters, but Shaw can take advantage of Marcos Rojo's lack of recovery time following the Copa America to make the left-back slot his own. Daley Blind Part of Van Gaal's Netherlands team at the 2014 World Cup, Blind has plied his trade for United as a defensive midfielder, a left-back and now a central defender. Playing alongside a vastly-improved Chris Smalling, Blind looked a little unsure of himself against Spurs. Harry Kane gave him a difficult afternoon, and it's unclear whether Van Gaal is simply using the 25-year-old at centre-back until a new signing arrives. A good performance against Villa, and Blind may be able to push back his manager's recruitment plans until January. Wayne Rooney Within sight of Sir Bobby Charlton's goalscoring record for club and country, Rooney is the first name on Van Gaal's team sheet at the moment. Following the departures of Radamel Falcao and Robin van Persie, the 29-year-old is United's only recognised senior striker - unless Chicharito will genuinely be given a chance to prove himself. Rooney needs to hit the ground running to combat doubts over whether he can score the goals to spearhead a title challenge. Playing in a system that requires only one striker - and for a manager with little time for sentiment - even the captain can't guarantee that he'll be the main man in a few weeks' time. Ander Herrera Of the five player in this list, Herrera is the least likely to start at Villa. However, he remains a popular figure among fans at Old Trafford. After the dark days under David Moyes, Herrera's presence brought a much-needed injection of dynamism last season that had been missing in the United midfield for so long. He chipped in with goals, had an eye for a killer pass and closed the opposition down quickly. But to the bemusement of many, Van Gaal seems content to have the Spaniard warming his bench again. Perhaps an impressive substitute appearance against Villa might be enough time to change his mind.