Novak Djokovic slumped to a surprise fourth-round loss to Roberto Bautista Agut at the Miami Open on Tuesday.

The world number one has been below his best since winning the Australian Open and suffered a 1-6 7-5 6-3 loss to Bautista Agut.

Djokovic, a 15-time grand slam champion, was beaten in the last 32 at Indian Wells and his departure in Miami was also earlier than expected.

A six-time winner of the ATP 1000 event, Djokovic was up a set and a break before losing to Bautista Agut, who will face defending champion John Isner in the quarter-finals.

Bautista Agut beat Djokovic for only the second time in Qatar at the start of this year and that appeared to be fresh in the Serbian's mind as he dominated the first set.

Spaniard Bautista Agut made far too many unforced errors and the 22nd seed saved a set point to avoid a bagel.

It was looking ominous for Bautista Agut when he was broken in the first game of the second, but it was Djokovic who was disgruntled after he was pegged back at 1-1.

Djokovic continued to be frustrated as Bautista Agut fended off three break points to secure a battling hold in the next game and the world number 25 led 5-4 when rain halted play.

Bautista Agut saved a break point to take a 6-5 lead following the resumption and levelled the match when Djokovic netted a forehand off balance.

As the lengthy baseline exchanges continued, Bautista Agut and Djokovic traded blows, both serving double faults when break point down early in the third set.

The breaks continued as Bautista Agut took a 4-2 lead when Djokovic dragged a backhand wide.

Bautista Agut completed the job in the ninth game, a forehand winner down the line sealing his victory.