Manchester United manager Louis van Gaal says observers must be patient with Anthony Martial and Memphis Depay ahead of Tuesday's Champions League opener against PSV.

While 21-year-old Depay has had a mixed start to life at Old Trafford since his close-season move from the Philips Stadion, Martial marked his United debut with a goal in Saturday's 3-1 win over Liverpool.

The former Monaco striker could help fill the void left by Wayne Rooney's injury-enforced absence in Eindhoven but Van Gaal called for patience with the pair.

Asked about Martial's mood after his showing on Saturday, the former Ajax boss said: "I have only had one day of training after Liverpool, and then it was a light session.

"But [Martial's] impression was good, I can only say it's good but it's the same for Memphis. You have to give them time and that's what I am asking of the fans as well.

"He cannot change his market price. As a manager you are never satisfied but [Depay] is doing well, he's played every game.

"It's not easy, adapting to the rhythm of the Premier League but of course he has to adapt to that rhythm and there being a lot of pressure on the ball but he shall improve I think.

"I have to be patient with Memphis but also for [Jesse] Lingaard, [Andreas] Pereira, [Adnan] Januzaj - you can't demand players of 19, 20 and 21 that they are consistent. You have to accept that."

Depay will likely feature against his former club in this week's Group A clash, having come through the youth system at PSV before becoming a key part of Phillip Cocu's title-winning side last term.

"[Martial and I] are both young so we can help each other and ask questions," added the winger.

"It's the same with Luke Shaw - we talk a lot, he has played longer in the Premier League than me so I have a lot of questions for him.

"We can all help each other. I learned a lot [at PSV] but it's like what the boss is saying - it's on a different level, the competition is different so I have to learn in the Premier League and improve.

"Of course I've learned a lot from PSV but [the Premier League is] different."