Rashford broke the deadlock before setting up Rasmus Hojlund for United’s second as the Red Devils surged into an early two-goal lead away from home in the Europa League.
However, goals from Pepe and Samu Omorodion drew the hosts level at the break in a topsy-turvy encounter in Portugal.
Despite being one of United’s best performers in the first 45 minutes, Rashford was surprisingly brought off before the second half, with Alejandro Garnacho replacing him for the second half.
However, Ten Hag confirmed that the decision was not injury-related and merely a matter of rotation ahead of a hectic schedule for the Red Devils.
‘We have to rotate,’ he told TNT Sports. ‘We didn’t start Garnacho and he had a great game not only on Sunday but I think the whole season.
‘On Sunday we have another hard game, so we need players to be available and fit and fresh.’
Pressed on whether Rashford could have continued, Ten Hag responded: ‘We have to play Garnacho. We have a quick turnaround to Villa.
‘They have a day longer [to recover] and we have an away game [today] so we want fresh players on the pitch on Sunday.’
After the break, Porto took the lead as Omorodion found his second off the evening, but United’s blushes were spared in the dying moments when substitute Harry Maguire nodded home from a corner to rescue a draw for the visitors.
The result will do little to ease the speculation on Ten Hag’s future as United boss, but the under-fire Dutchman was keen to call for calm despite the result meaning he has now won just one of his last 10 games in Europe with the Red Devils.
‘We will get there. Don’t judge us in this moment, judge us at the end of the season,’ he said.
‘We are in the process, we will improve. We have had two seasons where we have reached finals, we will continue and fight.
‘You see the spirit and the connection between the staff and the team. The players are together, they have a strong spirit and they want to achieve. We have a good mentality but in some defending parts we have to step up.’
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