The Red Devils boss fielded a defence of Chris Smalling, Phil Jones and Daley Blind during the 5-2 win against the MLS side.
Eric Bailly, Axel Tuanzebe and Victor Lindelof then replaced the trio at half-time, showing off the strength in depth Manchester United have at centre-back.
After the match, Mourinho said: ”The most important thing for me was to compete. The second important thing was to feel the players on the pitch in a system where last season we only played twice.
"It is far from being our system but we were working over the last two days to try to improve, in case we decide during the season to play more matches with three at the back. So positionally it was good.”
It sounds as though the Portuguese boss may look to either a 3-5-2 or 3-4-3 formation at points during the next campaign if he’s looking to spring a tactical surprise.
They certainly have the players to make the system work.
And, with the north-west side also looking to secure the signings of Nemanja Matic and Ivan Perisic, the three at the back formation could prove a headache for opposition managers.
Click through the gallery above to see how Manchester United could line up in a 3-5-2 or 3-4-3 formation next season.
