But, having competed a permanent switch to Burnley, where he made his debut in Thursday night's goalless draw at Istanbul Basaksehir, Sean Dyche feels the former Shrewsbury man isn't on the wane - he has more potential to tap into at Turf Moor.
And, after helping the Clarets strengthen their hopes of progressing in Europe, he produced a number of key saves to help Burnley earn a point at St Mary's.
With only three new signings starting the match on both sides, this had a look of a game left over from last season and the performances only confirmed this sense.
"I am not rigid that I stick one formation or one way of playing", Hughes said.
"I felt he was fit to play a part, but looking back he hadn't actually had a great deal of time on the grass in pre-season". But he looked as fresh as a daisy. I mentioned before the window that we want people who are battling to play, not those where there are big gaps and some who are more starters than others.
Southampton rode out a sluggish start where ex-Saints midfielder Jack Cork had the ball in the back of the net, only for the strike to be ruled out for offside.
Four minutes later, McCarthy made his first major contribution with a fine save form Aaron Lennon.
Not quite the match suggested by the scoreline, this was an intriguing encounter that Burnley should have won, not least after a powerful first-half performance.
Hart foiled a close-range effort from Jack Stephens at the back post and produced a reaction save to keep out a glancing header from Mario Lemina.
The pick of his saves was denying former England worldwide Aaron Lennon from point-blank range, before he got down well to save Ireland global Jeff Hendrick's header at the end of the first half.