Novak Djokovic has been knocked out of the Cincinnati Masters, losing in three sets to John Isner.

Both players were evenly matched in the first set, but the American was able to edge ahead in the tie-break to secure a one-set lead.

The world number one looked more in control in the second as Isner appeared to be tiring, grabbing an early break before saving five break points on his own serve, to take the set 6-3 and level the match.

Once again, there was little between the pair in the third set, which looked to be heading to a tie-break, but Isner was able to break in the final game of the match to secure his place in the semi-finals.

Isner will face Juan Martin del Potro in the last four.