Djokovic beat Serbian countryman Dusan Lajovic 6-0, 6-1. He won on his first match point, whipped off his hat, tilted his head back, and raised his hands in triumph.
The joy was less because of the first-round victory - he is a two-time champion here, after all - but more because his injury didn't resurface.
"I thought it was good considering the amount of matches I've played. I mean, I (have) played probably six, seven matches since Wimbledon last year," said Djokovic, who next faces Borna Coric of Croatia. "So after two years, finally I can play without pain."
He came to the tournament with a 3-3 match record this year, losing his last three since the Australian Open. This month, he stopped working with Andre Agassi and Radek Stepanek, the latest in a series of coaching changes for the 12-time major champion. Djokovic stopped working with Boris Becker in December 2016, and fired longtime coach Marian Vajda shortly before bringing aboard Agassi.
Now, Djokovic has gone full circle and is working with Vajda again, albeit in an informal coaching capacity since they do not have a long-term agreement.
Djokovic sees him as part coach, part confidante.
"He's more like a brother, a father ... someone I can share a lot of things with, whether it's professional or private life," Djokovic said. "He's always there for me, knows me inside out. He knows what I need in order to get to the highest possible level of play."
Djokovic took the second half of last year off and then had a medical procedure in February. Then he lost his opening matches in March at Indian Wells - to a qualifier ranked outside the top 100 - and Miami.
"I might have rushed my decision to play a little bit," Djokovic said. "Playing well below the desired level, it wasn't easy for me to cope."
He touched upon his split with Agassi and Stepanek, insisting there was no acrimony.
"I didn't know in which direction I wanted to go after Indian Wells and Miami. I was questioning which way I want to move ahead," he said. "Nothing personal, no bad feelings. We just split in a very normal way. ... We're going to be seeing each other and still keep on being friends."
Kei Nishikori reached the second round by beating Tomas Berdych 4-6, 6-2, 6-1. He broke the Czech's serve six times and dropped his own twice.
Nishikori also needs time on court after only recently returning from a torn tendon in his right wrist. That injury ruled him out of the U.S. Open then the Australian Open.
The Japanese player, ranked 36th, came back in late February at the Mexico Open.
Nishikori said he felt a "little soreness" in his wrist against Berdych.
Other winners included Roberto Bautista Agut of Spain, Milos Raonic of Canada, Andrey Rublev of Russia, and Albert Ramos-Vinolas of Spain.
Ramos-Vinolas, who lost in last year's final, beat Jared Donaldson 6-3, 6-3. Donaldson ranted at the chair umpire over a line call and squared up to him as he continued to argue. The American received a code violation.
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