- Tag results for Jose Mourinho
Pogba's criticism comes shortly after it appeared that he and Mourinho were mending their rift.
The United manager saw a run of three consecutive wins, all of them away from Old Trafford, come to an end in lethargic fashion.
The right-back's debut was delayed while he recovered from knee surgery but he looked assured as he made his first appearance for the club in Champions League against Young Boys.
Pogba played a crucial role in France's path to being crowned world champions -- scoring a sublime goal in the final against Croatia -- in Russia in July.
Mourinho was once the Champions League's pre-eminent force, winning the tournament twice and making the latter stages virtually every year.
Luciano Spalletti's side return to the Champions League for the first time since the 2010-2011 season on Tuesday when they host Tottenham at the San Siro.
Rashford will definitely be missing when Mourinho's men travel to Watford on Saturday, though, as he begins a three-match ban after being sent-off against Burnley before the international break.
Romelu Lukaku opened the scoring in the 27th minute with a simple back-post header from an Alexis Sanchez cross.
Guardiola was asked about the pressure which is mounting on his United counterpart following consecutive Premier League losses to Brighton and Tottenham.
Now in his third season at Old Trafford, United might have already seen the best Mourinho has to offer.
The odds on Jose Mourinho losing his Manchester United job have been slashed in recent weeks as on top of adverse results.
Jose Mourinho is far from the only culprit with Manchester United's slide on the field dating back to Alex Ferguson's retirement in 2013.
Mourinho was in particularly dour and uncooperative mood ahead of his team's Premier League meeting with Mauricio Pochettino's Tottenham on Monday.
Manchester United, by contrast, look anything but living up to their name with divisions emerging between executive vice-chairman Ed Woodward, key players like Paul Pogba and Mourinho.
Mourinho's side were blown away on the south-coast as Brighton scored twice in two minutes thanks to goals from Glenn Murray and Shane Duffy midway through the first half.