Fletcher admits he was impressed by Donovan's loan spell with Everton.
He said: "I think that he was one of their best players when he was over here. I'm sure they would have been delighted to keep him for longer. Obviously, he had to go back, but there's been a lot of talk of him maybe staying there permanently.
"There's been a couple of English teams interested since then, but he was a real threat in the game - a lot of pace and intelligent runs. He scored some fantastic goals and yeah, he was a real handful when we played against him in the Manchester United game. Lots of energy and a real quick, exciting player...Obviously [the MLS has] a little bit of a slower tempo.
"I think weather conditions play into that. I think that the English Premier League is known as one of the fastest leagues in the world, but that didn't seem to bother him. After a couple of games he got used to the pace. He is, if not the best player in the MLS, one of the best."