Coach Joseph Gilbert takes Jenson Brooksby from childhood to ATP breakthrough

WATCH: Jenson Brooksby addressed the Hall of Fame Open crowd after reaching his first ATP final.

It seems like Jenson Brooksby has come from nowhere to become one of this season's big breakthroughs. Having starting below the Top 300 in the rankings, the 20-year-old American is now up to No. 126—and rising—following his run to the final of the Hall of Fame Open and wins on the ATP Challenger circuit.

But coach Joseph Gilbert, who has been working with Brooksby since he was seven years old, knows what a long climb it has been. The pair have been training in Sacramento since this now tall, big-hitting pro was a skinny junior.

"Between 16 and 18, 17, he really shot up," Gilbert told TENNIS.com. ''It actually was somewhat of an advantage, by being smaller, he kind of had to learn all the skills—he couldn't count on being bigger and stronger than everybody. He's always had really good hands, learned all the skills from when he was smaller, and now he's 6'4", 6'5"."

In some ways, adds Gilbert, he is still growing into his height.

It's been extremely fun, coaching a kid from seven to 20 years old. It's been an extremely long run, but it's just getting started. Joseph Gilbert, coach of Jenson Brooksby

"His serving's still not potentially as big as it could be, because he's still not fully developed," he said. "His second has a really good angle, because of the height, so it's hard to attack."

Brooksby's success on grass, though, did come straightaway—he had never played an event on the surface until Newport. Gilbert wasn't entirely surprised.

"We felt he would be very comfortable on grass," he said. ''It suits him. The ball stays lower and skids more, it's a finesse game. Jenson likes the feel a lot, so dropshots work, and redirection works, slice works.

"And he got to practice on it a day or two, he liked it. And then he was just so excited [to play], the crowd's good."

Brooksby had also shown his potential during the 2019 US Open, though he initially chose to go to college rather than turn pro, and then spent most of 2020 on the sidelines. But he's been making up for it this season.

"In 2019 he qualified for the US Open, and beat [former No. 4] Thomas Berdych in the first round," said Gilbert.

"At that time, he had to make a decision. He went for two months, and then coronavirus hit. He was already thinking about turning pro, and now he didn't get the semester in, and we felt he was ready—he'd got bigger and stronger. [But then] he got a lot of injuries. It was frustrating for everybody.

“But we worked on his weaknesses, spent time in the gym, and he was ready at the beginning of the year.”

Assessing the men's game, Gilbert places Novak Djokovic and Rafael Nadal at another level from the rest of the field.

"I still like Nadal and Djokovic, they're just playing a little bit of a different game. It's very high percentage, very disciplined, very risk-free, where the young guys like going for more aggressive, more attacking," he said. "And they're not physically dropping. And on top of that, they have the experience.

"But there's a lot of young guys in locker rooms and they're coming up. The returns definitely set the guys apart. It starts with the strategy and footwork, the returns, the discipline.”

There are no Americans currently 30 or higher in the ATP rankings, but young players are moving up, including No. 32 Reilly Opelka, No. 37 Taylor Fritz, and No. 47 Sebastian Korda.

"I feel like there are a lot of Americans in the Top 100, but that group hasn't got into the Top 30, Top 20, Top 10 on a consistent basis. But a lot are still young," Gilbert said. "Korda is very professional. I've gotten to watch Taylor quite a bit—tons of weapons, a really good game. But all those guys, there's a ton of talent.”

That group should soon include Brooksby, who is aiming to improve his ranking further by playing a full hard-court schedule—he did not receive a wildcard into next week's ATP event in Atlanta but will play the challenger in Lexington, then try to get a wildcard in Washington and the US Open.

"If he can make another run at one of these 250s or one of these bigger ATP events, it'll jump up. If he can keep it up, he'll keep moving forward,” Gilbert said.

And though they have been doing this for a while, Gilbert notes there's also a long way to go, saying, ''It's been extremely fun, coaching a kid from seven to 20 years old. It's been an extremely long run, but it's just getting started."