PARIS (Reuters) - Spain's Carlos Alcaraz reached the French Open third round but suffered a worrying loss of form midway through his match against Dutch qualifier Jesper de Jong before winning 6-3 6-4 2-6 6-2 on Wednesday.
The third seed was forced to work hard for a two-set lead under the Court Philippe Chatrier roof but 176th-ranked De Jong refused to be intimidated and extended the match as Alcaraz suffered a third-set slump.
An error-strewn Alcaraz continued to struggle as the first four games of the fourth set all went against serve with the 21-year-old becoming increasingly frustrated on court.
But Alcaraz regained some control in the nick of time to hold serve for a 3-2 lead and he broke De Jong in the next game as his gritty opponent finally began to run out of steam.
There was some relief as Alcaraz accelerated towards victory and De Jong netted a forehand after a little more than three hours to end an absorbing contest.
"I mean, I said many times every player can make you in trouble and you have to be focussed on every point, in every round, it doesn't matter about rankings," the Wimbledon champion said in his on-court interview.
"It's good for me to get some rhythm but I prefer to spend some less hours on court."
Alcaraz arrived in Paris having not played a tournament since losing in the Madrid quarter-finals a month ago, courtesy of a muscular problem in his arm.
That did not stop him blasting past J.J. Wolf in the first round but De Jong, who came through qualifying and then beat Britain's Jack Draper in round one, was a step up.
Making a mockery of the difference in rankings between the two players, De Jong went toe to toe with Alcaraz, matching the Spaniard's power at times and producing some silky touches.
Alcaraz dropped his first service game as De Jong feathered a superb drop shot but the Spaniard recovered impressively to dominate the opener with his extra firepower.
De Jong dug deep to hold serve throughout the second set and had a break point at 4-4 but could not convert it.
When Alcaraz then broke serve to move two sets ahead it looked like a routine victory was beckoning but De Jong raised his level and Alcaraz's dropped off.
An increasingly confident De Jong has Alcaraz worried early in the fourth set but ultimately his challenge faded.
Alcaraz will face either American 27th seed Sebastian Korda or South Korea's Kwon Soon-woo in the next round.