Semifinal day at the Gerry Weber Open saw Roger Federer navigate his way through an ace-filled onslaught at the hands of Ivo Karlovic, to move into yet another final in Halle. The day ended on a poor note for No. 2 seed Kei Nishikori, who had to retire early in his match with a calf injury — opening the door for Andreas Seppi to move into the biggest final of his career.

First up on Centre Court was defending champion Roger Federer, facing the ominous task of ace-machine Ivo Karlovic. During his quarterfinal win, the Croat had served 45 aces to take out No. 3 seed Tomas Berdych and set an ATP record in the process. In yesterday’s press conference, the World No. 2 was already expecting a match that would be very serve-reliant without a plentitude of rallies.

Their semifinal meeting turned out to be exactly that as Federer found it difficult to get a read on the Karlovic serve in the first set — winning just one point behind Karlovic’s first delivery. The Swiss himself didn’t have too many problems on serve either so the logical conclusion of the set was a tie-break; in it, Federer proved to be the more composed of the two as Karlovic double faulted down set point.

“It comes down to a shot here or there,” Federer said. “So, we are both mentally prepared, we’ve played so many breakers against one another and I think he was better in the set in the first set, I was better in the breaker. I guess I deserved it because I stayed calm.

“In the second set, probably I was better throughout the set and he was maybe a bit better in the breaker. Maybe I got a little bit lucky in the breaker. So, it was a tough match. I knew that going in…I was struggling to read his serve in the first set but handled it better in the second set. It was tough.”

In the second set, Federer got more of Karlovic’s first serves back into play but once again neither player broke serve, forcing the top seed to clinch the match in another tiebreak. When asked about the process of “reading” a serve as big as the Croat’s, the seven-time Halle champion played it tight to his vest at first but then talked about it in greater detail.

“Well, I don’t want to say exactly what I’m doing!” Federer laughed. “But it’s true, it can be the ball toss, it can be the stance of the serves and it can also have something to do with the way you return. Sometimes, it depends on whether you’re able to analyze and pick out a couple of spots he’s serving to or where you generally tend to move to…”

“The problem is that he’s not serving the same way all the time. He’s mixing it up and sometimes his timing on serve diverges from my timing on return which might see it rain down aces for a short while.”

Overall, the 34-year-old was content with his performance, particularly the way he made the right decision in the tie-breaker.

The second semi-final turned out to be a short-lived match as Nishikori had to retire down a double break in first set at 1-4*, paving the way for Andreas Seppi’s first ATP 500-level final. The Japanese came on court with heavy strapping on his left leg and his movement was visibly impaired by a calf issue he picked up yesterday.

For Seppi, it’s the second time in a row that he has won a match after his opponent retired and while he was happy to make the biggest final of his career so far, he also talked about the “weird” experience of seeing his opponent having to shake due to injury twice in a row.

“Yeah, it’s a weird situation, I can’t even say that much about it because it’s the first time it happened to me,” he said. “We’ll see how it goes tomorrow after two abridged matches. But I already played a lot on grass in Stuttgart last week and played two good matches here in the first and second round — the Robredo match was longer than two hours. At least I’m not lacking in matchplay overall.”

Seppi said that he had no idea that World No. 5 was struggling with any sort of injury, but that Federer had popped into the locker room five minutes before the second semifinal was scheduled to start.

“No, I actually didn’t know anything about it until five minutes before the match,” he said. “Roger coincidentally came into the locker room and asked whether Kei was going to play and I had no idea why he shouldn’t play. [Federer] then said ‘Ah, no, never mind, it was just a question, I’m out of here,'” Seppi said with a chuckle.

“I didn’t quite know how to react to it. When I walked on court I noticed that his calf was taped and right away from the first service game it was evident that he…wasn’t at his best.”

Naturally questions surrounded Nishikori after the match: Was the calf issue he picked up during his quarterfinal win over Jerzy Janowicz going to affect his Wimbledon preparation or participation?

“I felt it yesterday during the match and I fought through yesterday,” Nishikori said. “But today was a little pain this morning and I tried in the match, but couldn’t really move. So, I, especially with these guys with the injury it’s never easy to win…and I don’t want to take a big risk for Wimbledon. So, I retired from the match today. It just came suddenly yesterday. So, there is nothing I could do and it’s very unfortunate. But I’ll try to find a way to prepare for Wimbledon.”

“I don’t know [whether it will affect my Wimbledon preparation and participation]. I cannot say much because I have to see how it will be the next couple of days. I really will have to see how the pain goes. But I’m sure it’s going to be okay. It’s no big deal.”

Although he says it’s no big deal, the timing is certainly unfortunate for Nishikori who had begun to look less fragile over the course of 2015.

In his bid for an eight Gerry Weber Open trophy, Federer will face Seppi tomorrow at 1 p.m local time. The doubles final — featuring unseeded Raven Klaasen and Rajeev Ram and No. 2 seeds Rohan Bopanna and Florin Mergea — will follow.

Bis dahin — auf wiedersehen.