"He served for the match and I had to save lots of break points in the fourth and fifth sets".
Dimitrov fought back in a more competitive third set, but could not overcome his opponent with Verdasco ultimately winning 7-6 (7-4) 6-2 6-4.
"A hard one to swallow", a glum Djokovic acknowledged during a brief news conference, in which he delivered clipped answers and said he might not play during the upcoming grass-court season. "So it's going to be an wonderful challenge for me".
Thiem, who lost in the semis to Djokovic in 2016 and Nadal previous year, said he is now better-equipped to go all the way.
Djokovic, who lifted the title at Roland Garros in 2016, had numerous opportunities to level the match during the fourth set.
"First week, my goal is to get to the second week", said 23-year-old Keys.
Djokovic made a slow start in a one-hour opening set, which took longer than the entire match between American Sloane Stephens and Estonia's Anett Kontaveit that had preceded it on Court Philippe Chatrier.
Cecchinato and Djokovic know each other well: They have practiced together in Monte Carlo, where Cecchinato trains at a tennis academy and Djokovic has a home.
"It was an fantastic, high-level match", said Zverev. I struggled from the beginning.
"I'm just not thinking about tennis at the moment". He then held three set points in the tiebreaker but couldn't convert any. There were two more set points at 8-7 and 9-8, both coolly saved by Cecchinato, who never panicked in spite of his lack of Grand Slam experience.
While that was happening, Cecchinato was docked a penalty point for unsportsmanlike conduct after a lengthy argument with the umpire and supervisor for leaving the court without permission.
Djokovic roared back in the third set and did not give Cecchinato an inch taking it 6-1.
Djokovic won 144 points to Cecchinato's 140 in the end but was surprisingly less effective in the clutch plays, one particular area of his game that seemingly still needs recovery.
Djokovic, who underwent right elbow surgery earlier this year, is the 20th-seeded player in Paris, his lowest Grand Slam seeding since the 2006 US Open.
After fighting through three consecutive five-set match-wins, Zverev is still on track to be the first German men's champion at Roland Garros since 1937. He never won a match at a slam, and now maybe he's soon in the semi-finals. Many would have been hoping for a Nadal-Djokovic matchup for old time's sake.
Zverev said he will undergo an MRI to discover the seriousness of his injury. You know, for me, not having so many matches in the last period, this is great. There was no way for me. "Sorry, guys, I can't give you that answer".