"It could have been one of these days where their heads were down a little bit," Sir Alex told MUTV.
"But they played with good professionalism and they enjoyed it. They did well and showed good enthusiasm. I'm satisfied with the attitude of the players. It's a decent result for us."
Despite the need for goals, it took United 22 minutes to register a meaningful effort on goal - perhaps a result of over-anxiety inside Old Trafford.
"I think the optimism from the fans - even from ourselves - to score a lot of goals was perhaps a wee bit too optimistic," the manager explained.
"But we had a lot of chances, we played a lot of terrific football in the first half in particular.
"If we'd scored an early goal in the second half we would have fired the crowd up, fired ourselves up and made them doubt themselves a bit. But we didn't get that early goal and the game petered out."