Australia's Nick Kyrgios hammered 18 aces without a double fault and shook off back pain Sunday to beat Russia's 10th-ranked Daniil Medvedev 7-6 (8/6), 7-6 (7/4) and win the ATP Washington Open title.

The 24-year-old Aussie, who struggled with back pain throughout the opening set, claimed the $365,390 top prize and his sixth career ATP crown at the US Open tuneup event.

Kyrgios, 5-1 this year against top-10 rivals, won his second title after the year after Acapulco in March and will jump from 52nd to 27th in Monday's new rankings, his first appearance in the top 30 in 43 weeks.

"This has been one of the greatest weeks of my life," Kyrgios said. "I've made massive strides.

"This is a tournament I'm definitely going to play for the rest of my life."

In a match that featured no break points or deuces, Kyrgios won after 94 minutes with back-to-back aces, the last his tournament-best 110th of the week.

Medvedev, 23, was broken only twice in the week but lost his only sets of the week to Kyrgios, costing him a possible fifth ATP title. He will match his career-best ranking of ninth on Monday.

"I know how well Nick can play when he wants to play," Medvedev said. "This week, I think he wanted to play and it was tough."

American Jessica Pegula captured her first WTA singles title by ripping Italy's Camila Giorgi 6-2, 6-2 in the WTA final.

The 25-year-old daughter of NFL Buffalo Bills owner and natural gas magnate Terry Pegula took a $43,000 top prize.

Kyrgios, who beat Medvedev on Rome clay in May in their only prior meeting, could face him again in the second round next week at Montreal.

Kyrgios began grabbing his back after points early in the first set, stretching and twisting during a changeover. His running and service speed appeared hampered at times.

Medvedev took 24 of 25 points on his serve to reach the tie-breaker, Kyrgios shaking off his back issues to match him as neither faced a break point.

Medvedev led the tie-breaker 4-1 but Kyrgios leveled at 5-5 on a drop shot winner, then denied a Medvedev set point with a 124-mph ace, his seventh of the set.

Kyrgios followed with a passing forehand winner and took the set after 42 minutes when Medvedev sent a forehand wide, then received treatment from a physiotherapist.

They battled through the second set and tie-breaker with powerful serves -- Kyrgios won 84 percent of first-serve points and Medvedev took 88 percent -- but a forehand long by the Russian put the match on the Aussie's racquet and he blasted to victory.

Kyrgios asked a fan where to serve before his final ace, then fell to the court on his back after making the ace. He was also quick to set down the heavy trophy after hoisting it for the crowd.

- Pegula powers to crown -

Pegula's only other WTA singles final was last September at Quebec City, where she lost to France's Pauline Parmentier.

"Quebec hurt a lot," Pegula said. "It's something you have to fight through. You can't overthink it.

"This final I just felt like I was ready. I felt confident in that."

Pegula, ranked 79th but expected to reach a career-best 54th on Monday, broke early in each set and closed out matters just inside an hour with an ace.

"I got a little emotional. It was almost a relief," Pegula said.

"It's extremely gratifying. The journey makes it all that much sweeter because it's hard. I really pushed myself this week. It's amazing. I'm excited.

"Hopefully I can take the momentum and keep riding it."

Pegula improved to 3-1 overall against 62nd-ranked Giorgi, but they had not played since 2012.

Giorgi, a Wimbledon quarter-finalist last year, has overcome nagging right wrist injuries that limited her to only six prior tournaments this year.

It was Giorgi's first final since winning last year's Linz crown. The 27-year-old Italian's only other career WTA title came at Rosmalen in 2015.

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