World No.1 Novak Djokovic got his US Open tennis title defence off to a winning start with a topsy-turvy four-set triumph over Jerzy Janowicz at the Arthur Ashe Stadium.
The top seed prevailed 6-3, 5-7, 6-2, 6-1 to keep his bid for 10 straight semi-finals or better at the Flushing Meadows intact.
Hampered by knee and lower back injuries for the first half of the season, Janowicz came into the match at No.247 in the men's singles rankings and looking to reach the second round in New York for the first time since 2014.
With Djokovic holding for 3-2 in the opening set, the Serbian called for a physio to massage his elbow.
He went on to break for 4-2 and survived two break points when serving for the set, reeling off four straight points to take it when Janowicz pushed long.
Asked about his fitness and why he called the physio, Djokovic said after the match: "Hopefully as the tournament progresses, I'll reach my peak. It was just prevention. It's all good."
"It wasn't easy today playing against Jerzy for the first time," Djokovic said.
"He's a very potent player—powerful serve, big forehands. He's unpredictable really."
"Play well as he did in the second set and he makes a couple of double faults in a row in the important moments. It's really up and down. That's why it wasn't easy to keep the concentration."