The veteran defender starred in the Bombers' 33-point win against St Kilda on Friday night, blanketing Saints debutant Tom Lynch and setting up countless attacking forays with his 24 possessions.
Knights hailed the victory as his side's best performance of the season and said Fletcher's efforts went a long way to setting up the win.
“There’s been talk about capping rotations. I don’t want to do that because if we can rotate him three times a quarter when he’s 40 years old we might be able to get him through to there,” Knights said after the game.
“He is just an amazing footballer [who has] stood the test of time in the modern game. He keeps developing and evolving. He started with Lynch, went a little bit to (Nick) Riewoldt. He's just awesome.”
Fletcher was assisted greatly by fellow defenders Cale Hooker and Michael Hurley, who accounted for Justin Koschitzke and Nick Riewoldt.
Knights was full of praise for Hurley, who was particularly effective with 30 disposals and 13 marks.
"Michael Hurley's had a lot on his plate this year and he's just starting to get going, really," he said.
"What he showed tonight was great for the future and it's good for him and Cale to play on the great forwards that Koschitzke and Riewoldt are."
As pleased as Knights was with the Dons' third successive win against the Saints, he cautioned that his side needed to replicate their effort against every opponent, no matter its standing.
"We've played decent footy against high-ranked teams. Now what we've got to do is have the maturity to play well against teams ranked around us or lower.
"That's our challenge and another challenge is obviously to play better when we go interstate. It's not good enough just to play well against the good sides."
While David Hille was far from his very best against the Saints, Knights said his presence allowed Paddy Ryder (two goals) to play a more damaging, free-running role.
The Bombers did not emerge unscathed from the game with Alwyn Davey copping a knock to his shin late in the game. Scott Gumbleton will also be monitored carefully after he received a hit to his troublesome back.
