Sinclair, who also played for Queens Park Rangers and Manchester City, made the comments during Sunday afternoon’s Premier League game between Everton and Swansea City at Goodison Park.
Stones, an England international central defender, started the match and played for the entire 90 minutes, as the Toffees suffered a 2-1 defeat.
The 21-year-old, who can also play as a right-back, did not have a good game and took too long on the ball in the first half.
Sinclair believes that the former Barnsley youngster needs to change his game as opposition players have figured him out.
"John Stones biggest asset is his disguise, he looks like he will play a 35 yards pass then cuts back inside,” the former England international said on BBC Radio 5 live on Sunday afternoon.
“Players have started to read that and he has to change his play and keep it simple, go back to the two-touch game.”
Over the course of the 90 minutes, Stones took two shots, had a pass accuracy of 92%, created one chance, and made one interception, one clearance and one block.
Everton are 12th in the Premier League table at the moment with 29 points from 23 matches, eight points above Newcastle United, who are currently third from bottom in the standings.