Panesar took three for 39 in the second innings at Headingley and six wickets in the match in all as the hosts completed a 167-run third Test victory and with it secured an unbeatable 2-0 lead in the four-match series.
"As a finger spinner there is probably no-one to match him in world cricket at the moment - his control is very, very good," said Fletcher of Panesar, whose tally for the series now stands at 16 wickets heading into next week's fourth Test at the spin-friendly Oval.
After Panesar took eight wickets in England's innings and 120-run second Test win at Old Trafford, Fletcher was lukewarm in his praise of the Northamptonshire bowler saying the 24-year-old had to work on his fielding and batting as well as perform on less helpful pitches.
And the former Zimbabwe captain made it clear that Ashes-winning left-arm spinner Ashley Giles, currently out with a hip injury, could come straight back into the side on account of his batting and fielding even though most observers regard Panesar as the more attacking bowler.
But Fletcher said of Panesar: "He bowled very well again. This has been a different pitch to the one he did well on at Old Trafford, a lot slower."
And he insisted the first Sikh to play Test cricket for England had always been in the selectors' thoughts for the 'Ashes' defence, which gets underway in Brisbane in November. "We never said we weren't going to take him to Australia.
"There will be 18 players going to Australia and there was always a very good chance that he would be included. Now he is staking a stronger and stronger claim."
Also in contention is Sajid Mahmood, the Lancashire quick whose Test-best four for 22 against Pakistan at Headingley suggested he could fill the gap in England's bowling attack left by the injured Simon Jones.
"We have always been pretty confident in Saj," said Fletcher. "I've seen some real potential in him, especially considering who he is replacing in Simon Jones and what we need as a priority in Australia is to bowl them out twice.
"What also impresses me a lot about him as a quick bowler is that he tried things and if they didn't come off he didn't become reclusive on those attempts, he was happy to try it again.
"But the key thing is speed, I have always believed you have to have someone who can bowl at 90 miles per hour," added Fletcher of Mahmood, 24, who a few weeks ago was dropped from England's one-day side for collective figures of 21-0-173-3 against Sri Lanka.
Both Panesar, whose family hail from northern India, and Mahmood, the son of Pakistani immigrants, received backing from Norman Tebbit, the former Conservative cabinet minister and close ally of Margaret Thatcher, who 16 years ago caused controversy with his 'cricket test'.
Tebbit said one way to judge how well ethnic minorities had integrated into British society was to see which side they supported at cricket.
"What cheered me enormously was not only that Monty was playing so well for England, but the attitude of the crowd towards him," Tebbit told the Daily Telegraph. "I was cheering both for him and Mahmood."
Meanwhile Fletcher said the bowlers had benefited from the captaincy of Andrew Strauss.
But the coach indicated that all-rounder Andrew Flintoff - currently out with an ankle injury - would lead the team in Australia even though England great Geoffrey Boycott has said Strauss should retain the captaincy.
"Andrew (Strauss) is a really strong character and nothing has highlighted that more than the fact that being captain hasn't really affected him," said Fletcher after the opening batsman's 116 in the second innings at Headingley.
"Every time we meet as selectors we debate certain positions but at this stage we have spoken about Freddie (Flintoff) being a natural leader in Australia - we will have to talk more when the time comes."