They were jawing over an earlier incident Tuesday when Wawrinka backed off from serving to engage the umpire.
"Nothing special," Wawrinka explained. "Not a big deal.
"At the end of the day, it's an important match for both. A lot of tension over there, especially with first two tiebreak[s]. We both wanted to win, trying everything to win it, and that's it."
Wawrinka, who won his first Grand Slam singles title earlier this year in Australia, seems to have returned to form after a scratchy few months. Lopez, who won the warm-up event at Eastbourne, looked tired. Although the Spaniard managed to win two of three tiebreakers in his previous match against John Isner, he wasn't up to Wawrinka's level in the handful of critical moments.
Leading the first tiebreaker 4-3, Wawrinka blistered a pair of aces at 127 miles per hour and 134. An unreturnable serve closed it out. In the second session, another ace delivered him to set point. A horrific backhand from Lopez found the net, and Wawrinka was on his way.
His opponent in Wednesday's quarterfinal is the same guy he's been practicing with for years: fellow Swiss Roger Federer.
The seven-time Wimbledon champion had beaten Wawrinka in 13 of 14 previous matches, but in the Monte Carlo final, the chemistry changed. Wawrinka emerged with a three-set victory -- and a new way of thinking.
"Yeah, it's going to give me a lot of confidence about myself, knowing that I can beat him, doesn't matter where, on big stage," Wawrinka said. "But tomorrow it's going to be a different experience. First time on grass. First time Wimbledon.
"It going to depends a little bit on me, the way I'm going to play, the way I'm going to be aggressive on the court. I know that if I can do a good match, I'm going to have some chance."
Federer feeling it
Roger Federer beat Tommy Robredo the first 10 times they played, but something curious happened the last time out. Robredo upended Federer in the fourth round of last year's US Open. The pendulum swung back Tuesday when Federer mesmerized the Spaniard 6-1, 6-4, 6-4.
Don't look now, but the seven-time champion has strolled into the quarterfinals here for the 12th time. He's convincingly won 12 of 12 sets.
Strictly in terms of elapsed time, Federer's fourth match of the tournament was the most strenuous. But the 94-minute victory outside on Court No. 1 sets him up nicely for Wednesday's quick turnaround against fellow Swiss star Wawrinka, who beat Lopez in straight sets.
Federer, as clean and efficient as ever, has served 54 times in this event -- and held every time. He's the only player left in the draw who can say that. The No. 4 seed didn't face a break point until the very last game and saved it with an unreturnable serve. He's saved all eight in the tournament.
"Always excited to be in the quarterfinals here," Federer said. "Closer to the finish line rather than the very beginning. I feel like my game is right there. Things are exactly where I want to be."
Federer said that two hours later, watching the World Cup was where he wanted to be -- as Switzerland played Argentina in a round-of-16 match. Even with Lionel Messi opposing his favorite squad, Federer said he was optimistic.
"That's why we love sports, why we watch," Federer said. "You don't know what's going to happen."
The win was Federer's 71st at Wimbledon, moving him into a second-place tie with Boris Becker on the all-time list. Jimmy Connors is first, with 84.
Oh, Canada again
In the very first game, Nishikori actually broke Raonic, converting his sixth break opportunity. It was the first time Raonic's serve was broken in this tournament. And then ... nothing.
Raonic served the 24-year-old Japanese player off the court and wound up winning 4-6, 6-1, 7-6 (4), 6-3. He finished with 35 aces -- his fastest serve checked in at 141 miles per hour -- and 66 winners.
Nishikori admitted there wasn't much he could do with Raonic's serve.
"Not really," he said. "Yeah, that was the key of the game today. He was hitting good serves and too many aces. Mostly I have to guess because he has great both serves, first and second. He can hit spin sometimes the first and second serve.
"I tried everything, but I couldn't read his serve."
And so Raonic, 23, follows fellow Canadian Eugenie Bouchard into the quarterfinals at Wimbledon. He's only the second Canadian to reach that stage in Wimbledon's 128 years. And it happened on Canada Day.
Raonic politely said he wouldn't be doing any celebrating.
"It's a quick turnaround," Raonic said. "Unfortunately, to this point there hasn't been as much Canadian success, especially on the singles side in the men's. So all the things sort of come and go and you appreciate them, but you don't give them too much value because it's ambitions that are beyond doing what no Canadian has done before.
"It's about really trying to become the best player in the world."
Defending champions Bob and Mike Bryan found their way back into the quarterfinals with a convincing 7-5, 6-3, 7-6 (5) win over Juan Sebastian Cabal and Marcin Matkowski. The Americans will meet Julian Knowle and Marcelo Melo, who defeated Chris Guccione and Lleyton Hewitt in four sets ... Francis Tiafoe, the 16-year-old junior from the Washington, D.C. area, had never played on grass until about two weeks ago when he practiced at the Roehampton facility adjacent to Wimbledon. It didn't stop him from winning his first-round match, which carried over from Monday. Tiafoe, the No. 2-ranked junior in the world, defeated Martin Blasko of Slovakia 6-4, 3-6, 6-3.