Roger Federer was at his championship best Wednesday. Tactically astute and mentally ready, the Swiss superstar negated dangerman Ivo Karlovic in a 6-3, 7-5, 7-6(3) win to reach his seventh straight semi-final at The Championships.

The second seed, riding a 17-match winning streak on the back of ATP World Tour Masters 1000 Madrid and Roland Garros titles, withstood 23 aces from Karlovic’s racquet in a one-hour and 42-minute victory.

"I don't play him every week, so it's okay," smiled Federer, after facing a player who has hit 170 aces in five matches. "Otherwise, if all the guys would be serving like that, that would be tough."

Federer, a five-time former champion and runner-up to Rafael Nadal in a memorable final last year, hit 38 winners and converted the two break point opportunities he created against No. 22 seed Karlovic.

After 80 games unbeaten on serve at The Championships, Karlovic had his serve broken by Federer in the fifth game with two fabulous winning returns. In a move reminiscent of Andre Agassi, the 1992 champion, Karlovic began to wear sunglasses at 2-5 down in the opening set. Federer committed just three unforced errors in the 23-minute first set.

Federer sensed a chance to break again at 5-5 in the second set, hitting a smash, backhand return and forehand winner from 15/15.

The third set was totally dominated by serve, which was inevitably decided on a tie-break. Federer created a mini-break when Karlovic floated a backhand long and a backhand pass helped him reach his 21st consecutive Grand Slam championship semi-final. The 27 year old improved to 9-1 lifetime against 6’10” Karlovic.

Federer will meet 24th seed Tommy Haas of Germany in the semi-finals on Friday. "Against Tommy I have to play a good match from the start," said Federer. "As we saw [at Roland Garros] in Paris, it was brutal.  Yes, it's gonna be tough. But I'm happy to be back into another semi-finals. [The] 21st in a row - it's amazing. Let's see what happens now."

At Grand Slam level, Federer is now 117-0 against players ranked outside the Top 5. His last loss to a player outside the Top 5 at a Grand Slam championship was to No. 30 Gustavo Kuerten at 2004 Roland Garros.