Andy Murray through at Miami Open after win over Denis Istomin

Andy Murray booked his place in the third round of the Miami Open with a 6-3 7-5 win over Uzbekistan's Denis Istomin on Saturday night.

Having waited most of the week to begin his campaign in Key Biscayne after a first-round bye, the British No 1 overcame his frustration with a ball mix-up to beat his opponent in one hour and 38 minutes. 

Murray broke serve in the opening game of the match but any thoughts of brushing his opponent aside were shelved as Istomin battled to hold his next service game and tested Murray with an audacious array of shots before the Scot came through to lead 3-1.

Murray stepped up a gear in the remainder of the first set, though, accelerating through to take it 6-3.

Istomin then broke serve for the first time in a pulsating fifth game of the second set - a superb forehand winner down the line from Murray all but forgotten as an overhit drop shot allowed Istomin to set up break point with a neat cross-court clip.

Live ATP Masters Tennis

Murray saved that with a huge serve but could not kill the game off and was eventually broken - after arguing with the umpire when he believed he had been given a lighter ball from the women's tournament to serve with.

"That's unbelievable. That's one of the women's balls. I could have just hit a shot with it," he told the umpire.

Though the rogue ball was removed from play, Murray was clearly flustered and netted a groundstroke in the next rally to lose the game before giving the umpire another earful.

"It's not right. Do you know how different the balls are?" he asked.

He immediately broke back though and got away with an indifferent service game at 5-5 to leave Istomin serving to stay in the match.

But the world No 76 could not do that, with Murray forcing a match-point advantage which went his way when Istomin sent a forehand into the top of the net.

Murray, who takes on Bulgarian Grigor Dimitrov in the next round, told atpworldtour.com: "I was hitting the ball cleanly. It's just the shot selection tonight could have been better, I think."

"Dimitrov is obviously a top-quality player. He had a good win today, a tough win, against [Federico] Delbonis.

"We played here once before; I managed to win that one. I played a bunch of tough matches against him.

"I think the last one was in Cincinnati where he had a match point. He had a bunch of chances to win that one and I managed to turn it around.

"I know I'll need to play good tennis and be a little bit more disciplined than I was tonight."