Despite dominating possession, United struggled to make headway against a well-drilled Wolves team, who threatened to snatch a win at the end in a match that pitted Mourinho against his former reserve goalkeeper during his time at Porto, Nuno Espirito Santo.
A frustrated Mourinho said: "Not a good performance, not a good result". We are going to play better than we did but I think it's going to be a very hard season. That's the attitude I like my teams to have every match.
"They've had a lot of shots and we know that because of the numbers but they haven't scored a lot".
Mourinho confirmed Alexis Sanchez will start against Wolves despite watching from the bench against Young Boys as his replacement, Anthony Martial, scoring in the 3-0 win.
Prior to kick-off the home crowd enjoyed the sight of Alex Ferguson back at Old Trafford for the first time since his brain operation in May but the brief reminder of more successful days was soon replaced by the contemporary United.
'One team came as if their lives depended on it and one team was too relaxed, ' said the United boss.More news: Mourinho to be without five players for Wolves clash
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"Wolves, by the way they faced the game, I think they deserve it".
The issue of post-World Cup fatigue has been debated extensively be club managers, with Tottenham striker Harry Kane the most high-profile example of those struggling to replicate their best form. We started poorly, we started both halves at a low intensity.
"And bad results and bad performances, they make you look more exhausted, more upset, more ugly, more everything". "And I expect my team to play better than we did", the manager continued.
'Unless you are against weak opponents, playing at 30 per cent of your potential is not enough.
"I can't explain the difference of attitude because I never have a difference of attitude", he added. "We all know that is not the case (in the Premier League)", he said.
"Let's get better so we can play every week like this".