Federer, 36, downed Frances Tiafoe in the first round of the Swiss Indoors – putting on a serving masterclass in the process.
He sent down eight aces and didn’t lose a point on his first serve – winning 21 out of 21.
Federer also gave Tiafoe no sniff of a break point as he stormed to a 6-1 6-3 win inside 61 minutes.
On the Swiss legend’s stunning displays this season, Petchey told Sky Sports; “The serve has been one of the crucial factors to it. His accuracy has been sensational – especially in recent weeks.
“Arguably it’s been some of the best serving of his career in terms of how tight to the line he has been.”
Roger Federer is battling it out to end the year as the world no.1 after winning at the Australian Open and Wimbledon.
He is in action at the Swiss Indoors this week before moving on to Paris for an ATP Masters 1000 event which starts on Monday.
Federer is 1,960 points behind Rafael Nadal in the rankings with a tournament win in Basel earning him 500 points.
Nadal is currently sitting out this week with a right knee injury.