Manchester United are working on a "solution" to get the best from Radamel Falcao, says manager Louis van Gaal.
The Colombian striker, 29, has scored four goals in 20 appearances for the club since joining on loan from Monaco.
When asked about his form, Van Gaal said: "We are looking for the solution.
"You can give fantastic performances in another country but not in the country that you are present for. That is not the first example and it will not be the last example."
|River Plate (2004-09)||90||34|
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Falcao played for United's under-21 side against Tottenham on Tuesday after remaining on the bench for the FA Cup defeat by Arsenal 24 hours earlier.
The Dutchman claimed he did not put Falcao in the youth team as a "humiliation" and said the former Porto and Atletico Madrid forward had reacted to the decision in the right way.
"Falcao did not play his best match in the second team but he has tried his utmost best," said Van Gaal.
His loan is due to expire at the end of the season, after which United must decide whether to take up a £43.2m option to buy him.
Falcao, who earns a reported £260,000 a week, has started just two of United's last five games.
Van Gaal added: "In a club like Manchester United it is more difficult than in a minor club because here he has his competitors. Now Wayne (Rooney) is playing there and Wayne is scoring so you always have to compare players with each other but you need also luck."
United, fourth in the Premier League, host Tottenham, three points behind in sixth, on Sunday, kick-off 16:00 GMT.
And with games against Liverpool, Manchester City and Chelsea to come over the next few weeks, Van Gaal believes United can still finish second in the Premier League.
"The coming matches are very decisive," he said. "We are so close with a lot of clubs. We can be second or third. It is not a big difference, I believe.
"Manchester United has to be one of the teams who has to play in the Champions League."