Frustration got the better of me - Novak Djokovic

Novak Djokovic said his concentration lapse was the cause of his mid-match outburst, in his four-set win over Roberto Bautista Agut at the US Open.

The top seed eventually booked a spot in a quarter-final of a major for the 26th consecutive tournament via a 6-3 4-6 6-4 6-3, but his concession of the second set saw him lash out.

After the Spanish 23rd seed reeled off four straight games from 2-4 to level the match, Djokovic walked back to his chair and stomped on his racquet bag, snapping one of his tools.

The Serbian then trailed in set three 1-0, only to reel off three straight games to regain control - but the world number one still rued his lapse.

"I was upset with myself," Djokovic told a news conference.

"I was frustrated with the fact from 4-2 and 15-40 I wasn't able to capitalise on those opportunities and to lose five games in a row. I cannot allow myself to do that. It happens. I'm a player that shows emotions.

"Obviously at that moment it wasn't easy, but I managed to kind of regroup and use the experience of facing these particular situations before in my life, knowing what to do next.

"Important thing is that I managed to find a way to win."

Djokovic likened the unheralded Bautista Agut to another Spaniard, former world number three David Ferrer.

"I started allowing him to control the rallies. I didn't do what I did for set and a half, which was after few balls stepping in and taking control," the nine-time major winner said.

"If you give him an opportunity, if you drop your level, he's a kind of a player - similar to David Ferrer - that is going to get on top of you, which he did."