Goalkeeper Tim Krul says Newcastle United must improve their disciplinary record after two red cards in their first four Premier League games.
"We know it's not acceptable and we have to learn quickly," the Netherlands international told BBC Newcastle.
"It's hard enough with 11 players in the Premier League and to get two first-half sendings off makes it hard for us.
"We have to look at the positives, we've got a great group and spirit, real quality and we just have to get the first win."
Head coach McClaren was given the funds to strengthen the squad this summer, with Georginio Wijnaldum, Mitrovic, Chancel Mbemba and Florian Thauvin all arriving at St James' Park.
Krul said he had already seen the impact of a newly galvanised squad.
"Look at the bench. For me as a goalkeeper I thrive on top quality players in front of me," he added.
"If I see [Fabricio] Coloccini put a fantastic block in, Moussa [Sissoko] and Jack [Colback] tracking back, that gives me a lift.
"We thrive off each other, we did that last week [in the draw against Manchester United] and nearly did it this week [against Arsenal].
"The manager believes when we get that first win we can have something really special, it's no good talking about it we've got to show it."