Venus Williams plays first match since early January, loses to 17-year-old Celine Naef

The age difference was straight out of a recreational tennis league, but the shotmaking was undoubtedly professional.

On Tuesday, 42-year-old Venus Williams—playing her first match on the WTA Tour since early January, which she competed in Auckland—fell to 17-year-old Celine Naef, 3-6, 7-6 (3), 6-2.

"I cannot believe I had the chance to play against Venus," said Naef afterwards, per the WTA. "She's an amazing player and really a role model for anyone."

Naef, ranked No. 202 in singles, had only played ITF tournaments until May, when she reached the round of 16 at the WTA 125 in Florence. She attempted to qualify for Roland Garros, but lost her opener in straight sets to Elizabeth Mandlik.

Her win over Williams—nearly two-and-a-half times her age—recalls Coco Gauff's first-round win over the living legend at Wimbledon years ago. It is probably far less surprising given Williams' prolonged stretch of inactivity, and the decidedly lower-profile stage; but it may be as surprising, given Naef's near-complete lack of pro-tour credentials.

"For me, it was the biggest stage I ever played," said Naef. "It was incredible and amazing to play in front of such a big crowd. I was very nervous, maybe you could see, but I tried to keep going and try my best."

That crowd included Serena Williams, who retired at last year's US Open and is pregnant with her second child:

After saving break points and holding for 3-3, Williams broke Naef in the next game, then wrapped up the set with a love hold:

The sequence appeared to be repeating itself after Williams consolidated a break in the second set with a comfortable hold for 4-2. But a rushed, netted forehand from Williams while down break point at 4-3 gave the Swiss a lifeline, which she took advantage of.

Serving at 5-5, Naef held from 0-30—then proceeded to cover her face with a towel during the changeover.

"Not sure if she's supremely confident, or playing with fire here," the world feed commentator said during Naef's set-two tightrope walk.

Minutes later, after Naef aced Williams for a 3-1 lead in the eventual tiebreak, the commentator gave a different assessment: "You can see she's visibly grown in stature and confidence."

A Williams backhand error handed Naef the second set, and foreshadowed what was to come.

Venus, a five-time Wimbledon champion, is expected to compete in additional grass-court tournaments before the hallowed Grand Slam.