Even after a senior career lasting 24 years, Roger Federer is "nervous".
Speaking to Eurosport, Federer said: "People don’t think I am (nervous) but I haven’t played in forever and I hope my level is somewhat okay. My God, you know people probably expect me to play super top or a 'normal' level, but that's not going to happen.
"I really just hope it's going to be somewhat okay."
Roger Federer's "perfect match"
In the interview, Federer looked back on his career highlights and lowlights.
But what was the best match Federer ever played in his long career, which spanned 81 Grand Slam tournaments?
"For me (the most) special is the US Open final against Lleyton Hewitt where I win 6-0 7-6 6-0," Federer recalled of his inaugural triumph at Flushing Meadows in 2004 against Australia's Hewitt.
"It doesn't happen like this in Grand Slam finals that you take off like that for a set, (have a) little wobble in the second set, then you dominate in the third again.
"I showed the world that I was a deserving world number one, and against a guy who I respect so much. I feel like if I look back I was almost like to play that match again."
That was the first of five straight US Open titles Federer would win from 2004 through 2008.
READ MORE: Federer's Grand Slam career in numbers
Roger Federer: My biggest heartbreak
By the same token, Federer was asked to name the match he looks back on with the biggest regret, and unsurprisingly chose another Grand Slam final.
"Probably Wimbledon 2008," the Swiss star said immediately.
"Just because of the way it ended, in the darkness, with Rafa (Nadal). There was so much on the line it needed a winner and it went his way."
In that match, Nadal ran out to an early lead taking the first two sets 6–4 6–4. However, Federer dug deep to win the next two sets in tiebreaks, 7–6(5) 7–6(8).
The match, interrupted by two rain delays on Centre Court (the roof now on Centre Court was not yet installed), lasted 4 hours 48 minutes in play time and over seven hours in total before Nadal took an epic deciding set 9–7.
Federer added: "It was heartbreak, yeah."
READ MORE: Roger Federer's Wimbledon finals
Federer's proudest achievement
Despite all his on-court success, Federer said in retirement, he would be proudest of not what he achieved on court, but how he managed his life off it.
"I think I'm trying to be as normal as possible, as authentic as possible, and I always try to stay the same way for as long as possible," Federer remarked.
"(It's) not an easy thing to do in the public eye to be honest because there's cameras more and more now and it's hard to escape (for) private moments, but I feel I've managed that part really well and to stay happy throughout to be in that public eye.
"Of course I was really, really excited again going away from that public eye and just going home and being with my family, being with my friends and everything."
Finding that balance between being a sportsman and having a private life, Federer added, got him through his career.
"The moment I would leave the site or the match or the tennis court, I'd be the normal Roger and I think that's what kept me mentally sane throughout these last 25 to 30 years."