Fletcher was speaking after Solskjaer's young United outfit were put to the sword by Manchester City in the first-leg of their Carabao Cup semi-final at Old Trafford.
Speaking after the 3-1 defeat, Fletcher said: "Ole spoke before the game about their youthful energy the team had, but they were a bit naive and lightweight.
"The centre-halves were marking nobody so the midfield was overloaded. You would like somebody to take initiative, can somebody go in and engage.
"Sometimes you have to take responsibility. I'm sure Solskjaer would give his players responsibility.
"He has two experienced centre halves who have to realise they are marking nobody. They can see the young midfielders getting outnumbered all over the place.
"They have got a young, inexperienced team, they could do with some leaders, some experienced players, but the manager has got what he has got and they have got to develop some leaders within themselves."