The Red Devils signed James in a £17m deal from Championship side Swansea City in June to bolster their options in wide positions.
Ole Gunnar Solskjaer recruited Crystal Palace right-back Aaron Wan-Bissaka to replace Antonio Valencia in the Manchester United team.
James has already scored three goals in four games after the Welsh winger netted against Chelsea FC, Crystal Palace and Southampton.
Wan-Bissaka has proven a force at right-back thanks to his ability to get forward and his impressive tackling style.
James and Wan-Bissaka have been the two big positives from an otherwise disappointing start to the Premier League season for Manchester United.
Former Red Devils defender Irwin heaped praise on James and Wan-Bissaka for their impressive performances at Old Trafford.
“He’s a player that can play on both wings and can cut in on his left and right. I think we’ve seen that already,” Irwin told Man United’s website about James.
“He’s not afraid to run at players with his pace and you always want players like that to chip in with goals. But to score three in four is a really great start for him. Some of the balls he puts in, particular in the latter stages against Southampton last Saturday, were a joy to watch.
“He’s been brilliant.”
On Wan-Bissaka, Irwin added: “I saw him play for Palace quite a bit last year, and he only played for the Palace first team for 15 months.
“He spent [his younger] years as a right winger, so what surprises me is how good he is defensively. Not just the tackling, because we saw that last year and in the first four games of this season, but the positions he takes up are very good.
“You always worry about a winger when they transform into a full-back, it can take them a while to get used to that. He seems really good at that. Obviously he’s a young lad and has a lot to learn yet, but he’s been a real plus.
“Last year we conceded 54 goals in 38 games. That’s not really Manchester United, we’ve always been good defensively. We need to strengthen, which we have done, and we need to keep more clean sheets.”
Manchester United also signed England international Harry Maguire in a £80m deal from Leicester City in the summer transfer window to make the centre-half the most expensive defender in the world.
The Red Devils will take on Maguire’s former club in their next Premier League fixture at Old Trafford as Manchester United look to end a three-game run without a victory.
Manchester United have collected five points from four games.
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