Ronaldo was not in the squad for United in the midweek clash at Old Trafford, which they lost 1-0 to crash out of the competition at their first hurdle.
The Portuguese scored a few days ago in the Premier League against West Ham in a 2-1 away win, but Solskjaer named an entirely different starting lineup to rotate his players.
"We decided more or less before Sunday [to make changes]," he told Sky Sports.
"We need more players to get match fit. Alex Telles is back and has been training for a week. It will be a long season.
"Cristiano has come in and made a difference already, he wants to play as much as possible but I don't think it is possible," Solskjaer added.
"If you are going to be successful at the end, you need the whole squad and minutes to be shared out. A risk making so many changes but we have played some games behind closed doors and hopefully we find the rhythm."
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