Switzerland's Roger Federer celebrates winning his match against Croatia's Marin Cilic at 2016 Wimbledon Championships in London, Britain, July 6, 2016. [Photo/Agencies]

LONDON -- Roger Federer expects to take "one hell of a boost" having battled back from two sets down to overcome Marin Cilic 6-7 (4-7) 4-6 6-3 7-6 (11-9) 6-3 in the Wimbledon quarter-finals without any fitness concerns.

The 17-time major winner underwent knee surgery earlier this year, while a back injury forced him to withdraw from the French Open in May.

His bid for a record-breaking Wimbledon title looked set to be dashed when Cilic stormed into a two-set lead on Centre Court on Wednesday, but the Swiss showed immense character to turn the match on its head.

And coming through without any physical issues has raised the 34-year-old's confidence ahead of a semi-final against Milos Raonic.

"My legs and back were there and serving was key, plus mentally this will give me a hell of a boost," Federer said in his post-match TV interview. "I am really ecstatic I was able to make it into the next round.