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."