It was only 11 days ago when Alcaraz came out on top in his epic five-and-a-half hour French Open final against Jannik Sinner, and while this second round clash in London may not have reached those same dizzying heights on the hottest day of the year, the British crowd were still served up an enthralling battle on Thursday.
The world No.2 was never quite at his stellar best and was a break down in the deciding set -- but he showed his strength of will once more, stretching his winning run to 15 matches, the longest streak of his career, after a marathon three-hour 23 minute duel.
"3:30 hours? Were we on clay?" scribbled Alcaraz on the TV camera lens after being relieved to get through.
"It was a really tough battle that we had today," he added on the court.
"He's a great competitor and he showed how difficult it is to beat him."
Alcaraz, the 2023 champion, looked well in control as he eased to take the opening set, and after saving four break and set points at 5-4 down in the second he forced Munar to a tiebreaker.
The pair traded early breaks with neither player holding serve over the first four points, before a Munar double fault allowed Alcaraz to take a 5-4 lead. He smashed an ace but then hit a double fault of his own on match point.
Munar made him pay this time to force a deciding set.
After Alcaraz went 2-0 up, the French Open champion was broken in his next two service games and Munar grasped a 4-2 lead.
But Alcaraz was not done yet, and two more breaks of serve sealed a hard-earned victory as he continued his preparations for Wimbledon, where the Spaniard will be aiming to complete a hat-trick of triumphs.
"I'm proud of the level I showed today. It's just my second match on grass this year," Alcaraz said.
"There were moments I struggled a lot mentally and physically. I still don't know how I'm standing here. But I'm really happy I've given myself another chance in the quarter-finals."
Alcaraz will face either French lucky loser Arthur Rinderknech or American Reilly Opelka next up.
British No.2 Jacob Fearnley reached his first ATP Tour quarter-final with a 6-3 2-6 6-2 win over French qualifier Corentin Moutet, and will next face Alex de Minaur's Czech conqueror Jiri Lehecka, who beat Canada's Gabriel Diallo 6-4 6-2.
