MIAMI - Canadian Milos Raonic fell behind early Friday and was unable to prevent a quick exit from the Sony Ericsson Open tennis tournament.

The hard-serving Raonic lost his opening match 7-6 (7-5), 7-5 to India's Somdev Devvarman. The No. 31-ranked Raonic -- who earned his first career ATP title earlier this year -- couldn't get past his first hurdle at Crandon Park after receiving a bye.

Raonic said he came out feeling flat and never recovered.

"I was trying to overcome a lot of things," said Raonic, who grew up in Thornhill, Ont. "I wasn't playing my best, I wasn't feeling the ball.

"I was trying to just squeeze by. I wanted to win today and use tomorrow to get better and play better Sunday. But that didn't happen. He played well. It was not the greatest match but I was there fighting as much as I could today."

Meanwhile, No. 2 seed Novak Djokovic improved to 19-0 this year by beating Denis Istomin 6-0, 6-1. The Serb lost only 20 points, two on double-faults, and needed just 48 minutes to advance.

Djokovic's winning streak is the longest to begin a year since Ivan Lendl started 25-0 in 1986. Djokovic won the Australian Open in January and the BNP Paribas Open last week.

"I know it has only been a couple of months of the year," Djokovic said, "but I have been playing great, and I want to keep on doing that."

Earlier in the day, Scotland's Andy Murray lost to American qualifier Alex Bogomolov Jr., 6-1, 7-5. Murray hasn't won a set in three matches since he was routed in the final of the Australian Open by Novak Djokovic.

Raonic, 20, fought valiantly in an opening set that lasted for more than an hour.

He rallied from 5-1 deficit after a shaky start. Raonic won the eighth game, saving four set points to break Devvarman and cut his deficit to 5-3.

Raonic recorded two more breaks to send the set into a tiebreaker. However, after falling behind 5-1, Raonic rallied to make it 5-4 and saved a fifth set point before Devvarman took the marathon when Raonic sent a backhand into the net.

Raonic earned a break in the third game but lost that advantage when Devvarman registered a break of his own to tie it 4-4. Devvarman earned another break to go ahead 6-5 before serving out the match in exactly two hours.

Raonic registered 14 aces with seven double faults and had 36 winners. He only converted three of his seven break opportunities.

"I was making a lot of mistakes, not moving," he said. "I felt half a second slow, and that makes big difference.

"The instinct was just not there. I was hitting OK but not doing the right things otherwise."

Raonic, who has been on the road since the start of the year, admits burnout has crept into his mentality.

"It's been 10 days since I played a match (third-round loss to Ryan Harrison at Indian Wells) and in those days I've been training hard.," he said. "I've not been home for awhile and it's starting to wear me down a bit.

"I'm mentally tired. On court I was flatter than in other matches this year. Right now the job is to go back home, recover and get ready for the clay swing (which begins in just over two weeks in Monte Carlo)."

Murray, seeded fifth, lost his opening match at Key Biscayne for the fourth time and for the second straight year.

"I was trying to get myself back into the match, trying to find ways," Murray said. "But I just didn't have that spark."

The Scotsman hasn't won a set in three matches since he was routed in the Australian Open final by Novak Djokovic. He has lost nine consecutive sets, a remarkable drought for a player ranked fifth in the world.

"The same thing happened around the same time last year," Murray said. "I have been practising well, training well, and then in the matches can't get anything going."

A year ago Murray lost opening-round matches in back-to-back tournaments, including at Key Biscayne as defending champion. This swoon is worse, with consecutive defeats against players ranked outside the top 100.

Donald Young was ranked 143rd when he upset Murray two weeks ago at Indian Wells. Bogomolov is ranked 118th, and his only other win over a top 10 player came in 2002, his senior year in high school, when he beat No. 3 Tommy Haas in Los Angeles.

Born in Moscow, Bogomolov moved to the United States at age 11 and lives in New Jersey. He has never been ranked higher than 97th but has played well this year on the minor-league circuit.

An hour after his big victory, Bogomolov said the news had spread quickly.

"I was just checking the 20 text messages I received from people I haven't heard from for 20 years," he said.

In women's action, defending champion Kim Clijsters downed qualifier Anastasiya Yakimova 6-1, 6-1.

Clijsters, the second seed, is playing for the first time since retiring two weeks ago in the fourth round at Indian Wells with a right shoulder injury.

"It's not fully healed, but it's healing," she said. "After Indian Wells I was pretty worried. Now I feel that I'm almost able to do everything that I want."

Yakimova committed 17 unforced errors Friday and had only one winner in the 50-minute match.

The last American in the women's draw was eliminated in the second round when Varvara Lepchenko lost to Petra Kvitova 6-1, 6-2.

Reigning French Open champion Francesca Schiavone advanced by beating Angelique Kerber 6-4, 6-4. No. 3-seeded Vera Zvonareva rallied to defeat former No. 1 Dinara Safina 3-6, 6-3, 6-2.

In other men's play, Americans Mardy Fish, Sam Querrey, John Isner and James Blake reached the third round. Fish, seeded 14th, won his opening match against Julien Benneteau, 6-4, 6-3. Querrey, seeded 19th, eliminated Mikhail Kukushkin 6-3, 6-2. Isner, seeded 30th, beat Igor Andreev 6-4, 5-7, 7-6 (2) and will face Bogomolov next.

Juan Martin del Potro took another step in his comeback from right wrist surgery by edging No. 29 Philipp Kohschreiber 6-7 (3), 6-4, 7-5.

No. 9 Fernando Verdasco lost to fellow Spaniard Pablo Andujar 3-6, 7-6 (3), 6-4.

No. 4 Robin Soderling earned his 20th victory this year -- most on the men's tour -- by beating Ivan Dodig 3-6, 6-2, 6-4.