But the 22-year-old, considered among the most gifted players of his generation, fired a total of 20 aces, including six in the first set, which he claimed in 30 minutes.
Andy Murray overcame an error-prone second set to beat Russian Andrey Kuznetsov in the first round at the French Open.
The 18th seed fired down 20 aces and 40 winners to register a 6-3, 7-6 (4), 6-3 victory over the experienced Kohlschreiber in a thrilling opening-round clash that lasted nearly two hours.
No. 7 seed Johanna Konta of Britain bowed out with a 1-6, 7-6 (2), 6-4 loss to 109th-ranked Hsieh Su-wei of Taiwan. Considering the setting, the result is not all that surprising: Konta has now lost all three matches she's played at the French Open over her career. "I think his strategy was to force me into using the backhand, and he was able to see that it was no longer my weak point and that I was able to use my backhand quite well", del Potro said about Pella, a Davis Cup teammate. And I think it was hard for him on the other side.
"I feel like my game, I know what to do to win matches".
That part of his anatomy - not the tender hip that has bothered him on and off in recent months - is the area that will receive the most scrutiny as the imposing and often volatile Australian moves through the draw in Paris.
"You sometimes play bad". "There is no regrets".
"I told you exactly where the ball hit", Garner replied. "I hope to go deep (into the tournament) this year". Nick Kyrgios believes the French Open is Rafael Nadal's to lose and that his generation will have to wait a little longer before releasing the old guard's grip on men's tennis. That's the way it goes.
"The world doesn't stop now. I'm always going to be confident", said Kyrgios ahead of his tournament opener against Kohlschreiber on Sunday. It's not the end of the world, OK?
Juan Martin del Potro made a winning return to Roland Garros after five years away, beating fellow Argentinian Guido Pella in straight sets.
Surgery to both wrists - the left wrist is now more problematic and affects his drive backhand - have robbed the 28-year-old of vital years on the circuit and last week he wasn't sure of competing at the French Open because of shoulder and back problems.
Swiss third seed Stan Wawrinka was a straight sets victor over Jozef Kovalik of Slovakia winning 6-2, 7-6 (6), 6-3 with few issues.
Wawrinka started his clay season poorly before emerging with a title at the Geneva Open last week.
Spain's Fernando Verdasco finished off his upset of ninth-seeded Alexander Zverev 6-3, 3-6, 6-4, 6-2 in a match that was suspended of darkness on Monday.
"It's good to see these young guys doing well but I'm just worrying about trying to get my body right to play", Kyrgios said ahead of his tournament opener against tough German Philipp Kohlschreiber. Yeah, I mean, I feel like I got, obviously, added motivation to play at a Grand Slam, for sure'. "I'm feeling good, I'm playing good tennis and I'm happy to be back in Paris".