By Mark Poulose

KEY BISCAYNE – The 2015 season has not been kind to top-ranked American John Isner, who rolled into the Miami Open with just five wins under his belt. Before playing at Indian Wells last week, Isner had lost four straight contests, including two Davis Cup matches against Great Britain. Yet, the 6-foot-10 American may have changed the tune of his subpar 2015 campaign on Monday.

Mired in a season remembered thus far by his inability to win matches, the lanky Isner electrified the Crandon Park Tennis Center crowd Monday night with a rousing 7-6 (2), 6-2 upset over ninth-seeded Bulgarian Grigor Dimitrov.

The win was the 250th of Isner’s career, a remarkable accomplishment for a latecomer to the tour.

“In a weird way, that devastating Davis Cup week [against Great Britain] opened my eyes a little bit,” said Isner. “I felt like even though I lost two matches out there, which was one of the lowest points of my career, in a way it turned my season around a little bit.”

This year, Isner has yet to string together a three-match winning streak and has seen his ranking fall to 24th in the world. His 5-6 start in 2015 was quite unexpected, as he has been a stalwart in the top 20 the past five seasons, and the top-ranked American for the past three.

“I still don’t have that many wins under my belt, but my level [of play] is there. I’m playing better than my record indicates this year, that is for sure.”

It was the first tour meeting between Isner and Dimitrov. Isner, equipped with one of the most dangerous service attacks on tour, powered his way through the defense of Dimitrov.

Dimitrov, nicknamed “Baby Federer” for his deft touch and seamless transitions from defense to offense, was unable to find his rhythm for much of the match against the big serving Isner.

The 6-foot-10 Isner sought to end points quickly with his monstrous serve and big forehand, hitting 30 winners compared to just 12 for Dimitrov. The Bulgarian struggled against Isner’s serve all night, forcing just two break points and converting none.

Isner, who has not been broken at this tournament, bullied his way to winning 82% of points on his first serve, and closed out the match cracking a 142 mph ace.

“To be honest, he didn’t play his best tonight. I know that,” Isner said. “But, you know, he is such a talent and he’s so young… I don’t believe he played his best tonight, but I feel like I had a lot do with that, as well.”

The match was Isner’s first at stadium court.

“I was a little nervous at the beginning. I haven’t played at night here; hadn’t played on center court yet,” he said. “Everything is different.”

Yet, the nerves did not seem to affect him. After taking the first set in typical Isner fashion, the big serving American broke Dimitrov twice in the second set, displaying an arsenal from the baseline he has yet to show this season.

“After winning the first set… I relaxed a little bit. He started to give me a little bit of errors,” Isner said. “His errors combined with me gaining some confidence out there [are] what ultimately allowed me to win that second set.”

It took just 29 minutes for Isner to win the second set, and 76 minutes to win the match. The win propelled Isner to the fourth round at the Miami Open, tying his career best mark at the event in just his eighth appearance.

Isner will next face big serving Canadian Milos Raonic in the fourth round. It will be his first chance to set a personal best at the tournament.