Rooney and Ibrahimovic have started all five of Man United’s games this season, managing a combined six goals and three assists.
However, the two have struggled to inflict constant damage and notably stagnated as a pair in the 2-1 defeat to Manchester City.
Jenas believes deploying the two in attack precludes United from unleashing energetic attacks.
“I don’t think Mourinho knows his best XI yet, and possibly the derby came a bit too soon for his team, because it looked as though Guardiola has progressed a lot further in developing his side,” he said.
“As a contest, it wasn’t even close; it was a battering, and the scoreline flattered United in the end. City’s squad looked light years ahead of United’s, and I think Mourinho has several decisions to make.
“When Rooney and Zlatan play together, I don’t think United have enough energy. You can’t ask Zlatan to go chasing full-backs; his game is about holding the ball up and bringing others into play.
Zlatan’s job in this United side is simple: to score goals. And as the Swede sits prettily alongside Diego Costa and Michail Antonio as joint Premier League top scorer, he can be happy with his work.
The case of Rooney, however, is slightly more problematic. As a No.10, all attacking movements streamline through the captain, meaning that the 30-year-old’s tempo somewhat dictates the tempo of the side overall.
And as Rooney’s immobility and lack of agility continues to mount, it seems as if United’s attacking quartet will be heavily impaired for as long as the Englishman forms its axis.