The 25-year-old recently joined the Black Cats in a £12m transfer from Wolverhampton Wanderers and scored twice on his league debut against Swansea City last Saturday.
Saha, who himself signed on at the Stadium of Light this summer after being released by Tottenham Hotspur, has been impressed with Fletcher's start on Wearside and expects him to get even better throughout the season.
"I feel respect for Steven. I am not surprised at all [with his start]," said Saha.
"This is just Steven's first few games and I think we can expect even more from him.
"That is a good prospect. I don't think this is the last time we will be talking about him."
Saha has yet to start a match for Sunderland, but made a substitute appearance in their 0-0 draw with Arsenal on the opening day of the season.