Manchester United's Marouane Fellaini scored his first goal in October 2014 - 13 months after joining the club

Marouane Fellaini has become a key player in Manchester United's bid to secure a Champions League place, says manager Louis van Gaal.

The Belgian midfielder has had [Only registered and activated users can see links. ] since David Moyes paid former club Everton £27.5m to make him [Only registered and activated users can see links. ] in 2013.

But Van Gaal says the 27-year-old now cannot be dropped on his recent form.

"When he is playing like he is playing now, I cannot change him," insisted the United boss.

[Only registered and activated users can see links. ] in pre-season after he finished his debut season, which was hampered by a series of injuries, without scoring in 21 appearances.

But he has started the Reds' last four games and scored three goals for Belgium in the recent international break including the only goal in a 1-0 win over Israel.

"From the first training session, he did what I asked of him," said Van Gaal. "I said 'you have to do this, or do this differently' and he was open and wanted to perform that, I'm not surprised [by his performances].

"He's had an unlucky season because he was injured and ill a lot of times, but when he's been fit he's always played for me, more or less. I was looking for balance in the team, and he can bring that."

Van Gaal has not completely ruled United out of winning the Premier League title despite being eight points behind leaders Chelsea.

"Mathematically, we can still do it," he said.