Despite the 2011 and 2014 Wimbledon champion being vastly more experienced than Sasnovich _ who has never been beyond the third round at a Grand Slam _ Kvitova was the one overcome by nerves in the deciding set.
However, Wozniacki still can't seem to get comfortable at the All England Club - especially when there's a swarm of bugs flying around her head.
Federer delivered a Centre Court masterclass lasting 89 minutes as the Swiss star hit 48 winners and 16 aces in his 6-4, 6-4, 6-1 victory.
No such problems for Federer, who won 35 straight points on his serve on route to beating Lukas Lacko of Slovakia 6-4, 6-4, 6-1.
In total, the eight-time champion lost only nine of 61 points on his serve and broke Lacko five times, including with a forehand victor to close out the match.
"I think it is important that, when you want to serve well, your point-for-point mentality is right", Federer said. "Some players can play best tennis".
The 27-year-old from Thornhill, Ont., leads the ATP Tour in the past year with wins in 73.7 per cent of his tiebreaks, a trend Raonic continued in his second-round victory.
Kristina Mladenovic advanced to a Wimbledon third-round meeting with Serena Williams after defeating Tatjana Maria 6-2, 6-2.
The top-seeded Halep, playing her first match since winning the French Open, recorded a comfortable 6-2, 6-4 win over Japan's Kurumi Nara.
Five-time champion Venus Williams once again dropped the opening set but again dominated the rest of the match to win.
In the first round, she started by conceding a tiebreaker against 58th-ranked Johanna Larsson before taking 12 of the last 15 games.
Asked if her wealth of Wimbledon experience was a key factor, Venus said: "I'd love to have that extra advantage". "If it's not two sets, then go to Plan B".
Former world number one Karolina Pliskova finally made it to the third round on her seventh visit to Wimbledon after seeing off two-time Australian Open champion Victoria Azarenka 6-3, 6-3.
American Jack Sock, seeded 18th, was up by two sets but still lost 6-7 (5), 6-7 (3), 6-4, 7-5, 6-2 to Matteo Berrettini.