The Dutch coach has experienced a tough Premier League baptism following his appointment as David Moyes’ permanent successor last May.
Van Gaal has successfully guided the Red Devils into the Premier League’s top four, although United have already exited both domestic cup competitions.
However, former Republic of Ireland international Irwin isn’t overly concerned the modest progress made by United in the 63-year-old’s first season.
Speaking to Sportsmole, Irwin said: “We had an unbelievable run of success under Sir Alex and there was always a worry that when he left, there was going to be a bit of a dip. The thing for us, and it seems strange to say this, is just to hang in there and finish fourth.
“After that, they need to build on the back of that. It’s a time for change and I’m sure some players will be coming in this summer and others will be leaving.
“The manager did not arrive until mid-July and the pre-season tour came around quickly, but went very well. He played a lot of youngsters and they beat some big teams – Real Madrid, Roma and Liverpool. After that, it was straight into the Premier League.
“He’s new to the Premier League and you learn all of the time. I’ve got no doubt that we will get stronger and stronger over the coming seasons.”
United have won just 16 of their 29 Premier League games under Van Gaal this season.
The 20-time English champions, who haven’t won a major trophy since their league success in 2013, make the short trip to Liverpool on Sunday.
Brendan Rodgers’ side can hoist themselves about United and into fourth place with victory at Anfield in the north-west derby.
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