(Updates with more details, results, quotes)
BERLIN World number three Roger Federer whitewashed German wildcard Mischa Zverev 6-0 6-0 in just 39 minutes on Friday to set up a Halle Open semi-final with fellow 30-something and defending champion Tommy Haas.
in a rematch of last year's final.
The 31-year-old Swiss, without a title so far this season, was in spectacular form on Halle's grass courts as he dished out a double bagel for only the second time in his career.
"I feel sorry for Mischa," said 31-year-old Federer, preparing to defend his Wimbledon crown later this month.
"This is not really how I want to win my games, it is a bit uncomfortable," added the five-times Halle champion who was runner up to Haas last year. "Now I need to switch from today's match to tomorrow's difficult encounter."
The 35-year-old Haas, who is shooting up the rankings after enjoying an injury-free season, had a much harder time against Frenchman Gael Monfils and battled into the last four with a 6-7(4) 6-3 6-3 win.
The former world number two failed to earn a single break point in the first set but twice got the better of Monfils in the next two sets as his serve improved and he got more aggressive.
A sizzling trademark one-handed backhand down the line gave the German a 4-2 lead in the third and the chance to serve out the match two games later.
"I managed to stay patient even after going a set down," Haas, up to 11th in the world after his French Open quarter-final run and his Munich victory in April, told reporters.
"It is these matches you are looking forward to," said Haas ahead of the rematch with Federer. "He is one of the best players of all time, maybe even the best ever but I am really looking forward to it."
Last year's victory was Haas' first against Federer since 2002.
Frenchman Richard Gasquet, a former Wimbledon semi-finalist, showed his skills on grass as he beat Germany's Florian Mayer 6-3 7-6(4) to set up a semi-final against Mikhail Youzhny of Russia. (Reporting by Karolos Grohmann; Editing by Clare Fallon and Pritha Sarkar)