Louis Saha thinks it could take a full year for Manchester United striker Radamel Falcao to adapt to the English game.

United pulled off what many regarded as the biggest coup of the summer transfer window last year when they signed Falcao on a season-long loan from Monaco.

Falcao arrived at Old Trafford with a reputation as one of the most feared strikers on the planet, but six months on he has scored just four goals.

Saha believes it may take Falcao 12 months to get used to the physicality of the English game, but whether he gets that time remains to be seen.

United have the option to buy Falcao for £43million at the end of the season, but with every poor performance from the Colombian, that seems more and more unlikely.

"When you are in a different formation or different management then you have to adapt. It could take three months, six months or maybe a year before you understand it," Saha said.

"It happens to even the best players.

"It happened to Patrice Evra here. For the first six months he was struggling. He didn't seem to understand the physical nature of the game in England. But he changed into a terrific player.

"Falcao is under pressure because of his contract. As a striker you want to score. When there is that amount of money involved you are under pressure."

Falcao's latest sub-par display came on Monday when he was substituted after an hour of United's 3-1 FA Cup win at Preston.

United improved after the former Porto striker was hooked and United scored three quick goals to snuff out any chance of an upset and advance to a quarter-final with Arsenal.

Louis Saha at United (GETTY IMAGES)

Falcao missed the World Cup due to a serious knee injury he sustained in January and since he moved to England, he has been troubled by a calf complaint.

Saha, who suffered his fair share of injury problems during his five years at Old Trafford, understands what the striker is going through, and is sure he will be a success at the club eventually.

"It is very hard. It is the hardest time in your life," Saha said when asked about the difficulty of returning from long-term injuries.

"You need to work with a team full of confidence. When I was coming back I had some team mate scoring goals every week so it was easier for me to adapt and just pick up some goals here and there. The pressure wasn't as big.

"I have sympathy with Falcao. I have no doubts about him. I know how hard it is to be a striker. There is always a lot of competition at this club.

"It is a battle. But he has the quality to do a great job here."

Saha, who scored 42 goals in 124 appearance for United, ducked a question on whether he thought United's final goal scorer at Deepdale, Wayne Rooney, had dived to win the penalty he converted.

The Frenchman was happy to see the skipper start up front though, rather than in midfield, where he has played a lot recently.

"I am a bit surprised he hasn't been playing as a striker. He can be very effective pretty much everywhere but he has always done really well as a striker," Saha said.

Van Gaal has been criticised in recent weeks for using Marouane Fellaini as a target man, but the big Belgian proved effective up front on Monday, scoring United's second from an Antonio Valencia cross.

Saha refuses to criticise Van Gaal for using direct tactics.

"I understand why United are playing in that way," he said.

"This season is all about winning games. The philosophy of the manager is to look at it at the end of the season. At the moment it is about results."

The FA Cup is the only piece of major silverware Saha did not win during his time at United.

None of the current squad have won the competition with United either but Ashley Young hopes this will be the year the trophy drought ends.

"We want to get back to winning ways and win this competition," the United midfielder said.