Federer already has three titles this year including a 20th career Grand Slam at the Australian Open in January.
However, he failed to defend his Wimbledon title earlier this month after he squandered a two-set lead to Kevin Anderson, who went on to lose to Novak Djokovic in the final.
Former British No 1 Henman reckons Federer will be back to his best on grass next year – even though the rest of the season may be a different matter.
“I think it’ll be hard for him away from grass courts,” Henman said.
“I think just as he gets older then the movement is probably the one element that becomes harder and harder but I still think, come Wimbledon next year, because it’s grass and he is the most attacking player, I still think he’ll have a great shot, as long as he stays injury-free and we all know the older you get the harder that becomes.”
Federer, 36, has been forced to manage his schedule carefully after missing the second half of 2016 with back and knee problems.
The Swiss seems to have given up clay-court tennis altogether and has today been forced to pull out of the Rogers Cup in Toronto despite having planning to join Rafael Nadal and Novak Djokovic there on August 6.
“I’m so disappointed not to play at the Rogers Cup this summer,” said Federer.
“I had a fantastic time in Montreal last year and always enjoy playing in front of the Canadian fans, but unfortunately with scheduling being the key to my longevity moving forward, I have regrettably decided to withdraw from Toronto this year.
“I wish the tournament every success and am sorry to miss it.”