The Red Devils laboured to a 1-0 win away to Real Sociedad on Thursday, depriving them of top spot in Group E by goal difference.
With five minutes to go, Ten Hag replaced goalscorer Alejandro Garnacho with Maguire, who - to no avail - played as a striker. The manager described the reasoning behind his decision as “clear” despite having Anthony Elanga among his bench options at the time.
He told reporters: “We needed the goal and then we went more opportune.
“With Cristiano [Ronaldo] and Harry Maguire, you have two good headers and we tried to go more direct into the box and I think we did several times, quicker to get into the box for the opponent.”
Ten Hag praised the performance of Garnacho after his first goal for United, as he underlined the injury issues impacting his attack.
“We need options,” the Dutchman told BT Sport. “We have problems there.
“Antony not available, Anthony Martial not available, Jadon Sancho not available, but I'm really happy with that performance and I hope he can keep the process going.
“He was a threat, he scored a goal, he was reliable defending so if you can keep this going I'm really happy.”