Tennis round-up: Osaka on why she split with coach Bajin

World No 1 Naomi Osaka was adamant that her shock split with coach Sascha Bajin had nothing to do with money but it was because she was determined that her career would not be about putting "success over happiness".

The German had guided the Japanese player to back-to-back Grand Slam titles as well as to the summit of the WTA rankings. But just two weeks after her triumph at MelbournePark, Osaka abruptly severed ties with Bajin. That led to suggestions the two had fallen out over money.

"Everyone thinks it was a money-related issue, but it wasn't," the US and Australian Open champion told the WTA in Dubai.

"That's one of the most hurtful things I've ever heard.

"I travel with everyone on my team, I see them more than my family. I would never do that to them.

"My reason is I wouldn't put success over my happiness -- that's my main thing. I'm not going to sacrifice that just to keep a person around."

Bajin, a former hitting partner of Serena Williams, Victoria Azarenka and Caroline Wozniacki, was named as the WTA's coach of the year in 2018 after his success with Osaka.

During their time together, Osaka rocketed from 72 in the world at the start of 2018 to number one last month.

Osaka said it was clear things were not right between them during the season's opening major.

"It was kind of brewing in Australia. I think some people could see that if they saw how we interacted," the 21-year-old added.

"I would not want to split on really bad terms. I'm not going to say anything bad about him because, of course, I'm really grateful for all the things he's done.

"During the Australian Open, I was just trying to tell myself to get through it. I'm not sure, but I think you guys noticed."

Osaka said she hopes to have a new coach in place by March at Indian Wells.

"It's not really ideal to go to Indian Wells without a coach. I don't want someone that's in the box saying negative stuff. That would be the worst," she said.

"(I want) someone that's kind of direct, not afraid to say things to my face. I'd rather someone say it directly to me than go around my back. That's one of the biggest things."

Kasatkina, Muguruza record nervy wins in Dubai

Russia's Daria Kasatkina roared back from a break down in the deciding set to beat Polish qualifier Magdalena Frech 6-3, 3-6, 6-4 in the opening round of the Dubai Duty Free Tennis Championships on Sunday.

Before arriving in Dubai, 11th seed Kasatkina had lost all four of the matches she had contested this season and on Sunday struggled for the majority of the match against Frech, who was playing only her second top 20 opponent.

Trailing 3-0 in the final set, Kasatkina struggled to land her shots and eventually finished with a whopping 61 unforced errors.

But the Moscow Open champion continued to back her aggressive approach and was rewarded when two consecutive forehands found the baseline to hand her a break in the seventh game.

Three backhand winners helped her fend off a break point at 4-4 before a string of powerful forehand ensured she claimed the final five games of the match to book a place in the second round.

Former World No 1 Garbine Muguruza was also forced to work hard for her 4-6, 6-3, 6-3 victory over Dayana Yastremska, recording her first win in three meetings with the Ukrainian teenager.

Muguruza put together a clinical performance, clinching eight out of 11 break points opportunities against Yastremska, who is the only teenager in the current top 50 at number 34.

The Spaniard will face China's Zheng Saisai in the second round.

Monfils overcomes Wawrinka to lift Rotterdam title

France's Gael Monfils overcame a determined Stan Wawrinka to win the Rotterdam Open 6-3, 1-6, 6-2 on Saturday, lifting his first title since January 2018.

In the first Rotterdam final between two unseeded players since 2008, Monfils raced past his Swiss opponent to convert two break points on his way to sealing the opening set in 36 minutes.

Three-time Grand Slam champion Wawrinka, who was playing his first final since undergoing two knee surgeries in 2017, fought back to clinch the second set but struggled to keep up with Monfils in longer rallies during the decider.

Despite winning his opening game to love, Wawrinka was broken by Monfils in the third game, while the Frenchman also maintained his service rhythm to dictate play in the final set.

Monfils, the 2016 Rotterdam runner-up, converted another breakpoint to go 5-2 ahead before he served out the match for his eighth career ATP title.

World No 33 Monfils, who reached the Sofia Open semi-finals last week, credited his practice partner Wawrinka for his resurgence, having lost just twice in 11 matches this season.

"You know this win is part of him," said Monfils, who last won an ATP title at the 2018 Qatar Open.

"We've been practising a lot, we've been talking a lot.

"... Sorry I beat you in the final. I hope we can have many more battles."

Cecchinato overwhelms home favourite Schwartzman in Argentina final

Italian Marco Cecchinato won the Argentina Open on Sunday with a clinical 6-1, 6-2 demolition of hometown favourite Diego Schwartzman.

World No 18 Cecchinato raced through the match in little over an hour to claim his third ATP title.

Buenos Aires-born Schwartzman buckled under the pressure of playing in front of a partisan crowd and at one stage lost seven games in a row.

Cecchinato romped to the title without dropping a set all week. The 26-year-old captured titles in Umag and Budapest last year and is now three for three in ATP finals.

"Winning my third tournament in my third final makes me happy," he said.

"I want to be physically good and train harder for the rest of the year. I know that I'll continue to have good results if I stay mentally solid.

"I was able to play a great match and was always focused. I followed the game plan from the beginning to the end. I improved my level yesterday and I was focused today, so I'm happy with how I was able to win the tournament."

Opelka earns first Tour title with New York win over Schnur

Reilly Opelka blasted 43 aces on the way to winning his first ATP Tour title with a 6-1, 6-7 (7), 7-6 (7) victory over Canadian Brayden Schnur at the New York Open on Sunday.

The 21-year-old American paved the way for the victory by successfully challenging what Schnur thought was an ace at 7-7 in the final tiebreak.

Schnur's shot was shown to be just out, so instead of having championship point the Canadian had a second serve, which he netted.

Opelka then slammed in his 43rd ace of the match for the victory. He had the same number of aces in beating top seed John Isner in their semi-final on Saturday.

"This is definitely what I’m most proud of," Opelka toldreporters.

"I was tough mentally, especially losing a lot of first sets this week, and my first serve really helped me out. I was able to play clutch in those big moments.”

Opelka easily won the opening set against Schnur but the Canadian rebounded in the second by saving two championship points in a tiebreak and claiming the set when Opelka double faulted.

Schnur had never won an ATP Tour main draw match before this week, and won two qualifying matches just to get into the tournament. "It’s a dream come true for me. This week showed that I belong in these big tournaments and playing against the top guys," Schnur said.

"It’s unfortunate the way it ended because I left it all out there and did everything I could, but that’s how sports go sometimes."