Federer cruises past defending champ Mayer into Halle semis

The world number 5, building up to an assault on an 8th Wimbledon title in July, will now face German fourth seed Zverev who saw off France's Richard Gasquet 4-6, 6-4, 6-3.

However, 21-year-old Khachanov rallied and force two set points which would have taken the match into a decider before Federer, an 18-time Grand Slam victor, closed out the tie-break.

Inside a minute, Federer, who skipped the clay-court season to prepare for grass after winning the Australian Open and titles in Indian Wells and Miami, broke Zverev to love.

In taking the opening set in just 24 minutes, Zverev already looked a beaten man and, even though he found a way past Federer in last year's semi-final, Federer ensured that a repeat was never on the cards. The 20-year-old German most recently crashed out in the first round of the French Open but has shown that he can perform against the top players with his Italian Open win over Novak Djokovic.

"I was a little uncertain about a player I don't know too well", he said of Khachanov.

"I think going into Wimbledon he's going to be probably the favorite to win the whole thing", Zverev said of Federer.

The Stuttgart defeat was the first time Federer had lost his opening match at a grass-court tournament since 2002 Wimbledon. He's playing really good tennis. "He hasn't had the best season so far, there is a lot riding on the match for him as well as for me because we both want to go deep into this tournament". Roger raced to a 4-0 lead, breaking Sascha in games 1 and 3 to gain the authority in the first set, and he sealed it with the third break in the game 7.

Khachanov, 21, also played 2017 quarter-finals in Barcelona and Lyon, while the 19-year-old Rublev will crack the top 100 next week in a rise from 106.

He would then come up against the brother of his opponent in the final Mischa Zverev in the second round and he would win in two sets, but was made to work hard for his win, eventually coming through 7-6 6-4.