There was little the goalkeeper could do to keep Romelu Lukaku out either as the striker doubled the scores in first half stoppage time.
The decision to make nine changes saw the home side toil against the well-drilled Royals and the Norwegian held his hands up afterwards.
"It's early days", said Solskjaer. "What we have asked them to do, the players have done", Phelan told Stadium Astro after the midweek win against Newcastle.
But Solskjaer's side closed out the match in a non-event of a second half to book their place in their fourth round and continue their momentum following the sacking of Jose Mourinho. It ties the record of Matt Busby, who also won his first five games in charge in the 1946-47 season. The Brazilian is rumoured to be frustrated and looking to leave the club, but more game time could convince him to stay put. I don't look at them and think we can't win that.
"I have had plenty of time to speak to them and not much time to train, so if any of the players think it's a holiday they're wrong". He took his goal excellently, rounding the goalkeeper easily before tucking away. I'm here to voice my opinion on that and I'm sure we'll sit down, me and Ed if we've got anything in the pipeline.
This match also highlighted the tinkering still required with VAR as the length of delay was nearly as frustrating as lack of communication inside Old Trafford before Mata scored from the spot.
"The squad travelled to Dubai after Saturday's 2-0 FA Cup win over Reading at Old Trafford for a training camp ahead of the Reds" next Premier League outing, against Tottenham Hotspur at Wembley Stadium next Sunday, 13 January'. Fred releases Lukaku, who looks to be one-on-one but can't quite shake Moore and then gets the ball caught under his feet.
"It was always going be hard with my team selection", Solskjaer said, after making nine changes to his team. Hopefully he'll be OK for next weekend. "When I came in they were open and honest".
"I'm not sure if Paul's going to be ready, he got a knock against Newcastle".