The 24-year-old sparked concern before kick-off after he appeared to suffer an injury during the warm up.
Pogba pulled up early after a short run and spoke to United assistant Rui Faria before heading back to the dressing room earlier than his teammates.
The France midfielder looked off the pace during the first half at St James’ Park and was brought off immediately after Matt Ritchie’s winning goal in the 65th minute.
But Mourinho maintains that Pogba did not have any issues and claims he wanted more ‘simplicity’ in his midfield by bringing on Michael Carrick.
Asked if Pogba was injured, Mourinho told Sky Sports: ‘No. No problems.’
And when asked why Pogba was brought off early, the United boss said: ‘I wanted a better way to come out in the first phase against a team that was defending in a very compact block.