Recapping all the action from Day 2 of the U.S. Open.

NEW YORK — The number “19” figured as important for Roger Federer and his first round American challenger Frances Tiafoe at the U.S. Open on Tuesday night.

Federer, who turned 36 earlier this month, arrived on court with years of experience that delivered a men’s record 19 Grand Slam titles to his credit.

Tiafoe, a talented American currently ranked No. 70 is just 19 years old, but seems poised to continue improving with each match played on tour. His ability to save a match point while breaking Federer’s serve at 5-3 in the fifth set will only serve to empower Tiafoe for the future.

When all was said and done, however, Federer showed why he is a champion for the ages.

Although he didn’t showcase his usually smooth on-court style, Federer managed to survive a 4-6, 6-2, 6-1, 1-6, 6-4 battle that lasted 2 hours, 37 minutes. The win, which came on his third match point, saved Federer from the fate of losing a first round Grand Slam match for the first time since the 2003 French Open.

“I think in many ways people were hoping for a great battle between a Next Gen (the name associated with the up-and-coming players) and an established player,” Federer said. “You don’t want to see a one-sided battle, so I think the people got what they wanted to see. And then at the end there was the drama.”

Federer is playing for the first time since reaching the Montreal final this month, where he was bested by Alexander Zverev of Germany. He then cited a back injury as his reason for pulling out of the Cincinnati tournament the following week.

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Tuesday’s five-set outing was an essential check on conditioning for Federer. As it turned out, he did appear to struggle at times in the match with his movement, but he was encouraged by the overall result.

“It was more than a test, it was a good one,” Federer said. “I think we both enjoyed ourselves. I had a bit of a slow start today. I was worried at the beginning with the back injury from a few weeks ago.

“To get through a five-setter you have to be OK somehow,” he added. “I’m really, really happy with tonight.”

It certainly didn’t always look as if this intriguing battle would go according to plan and land in favor of Federer.

Tiafoe often forgot his position as a virtual tour neophyte and clearly hoped to post the upset over the ever-popular Federer. The Maryland native managed to push Federer on numerous occasions, and possibly with more familiarity playing big-time matches might have moved on to the second round.

“I want to be No. 1 in the world,” Tiafoe said. “I want to be on the top of the game. He (Federer) told me I’m going to be a great player and that’s a great compliment.”

Until last year, Federer remarkably had what could be described as a…