Juan Monaco has caused an upset by knocking out US Open champion Marin Cilic in the second round of the BNP Paribas Open at Indian Wells.

Monaco was more ruthless than his Croatian opponent as he converted both of his break point opportunities in a tight first set which he claimed 6-4.

Cilic went a break down immediately in the second as Monaco attacked well from the baseline and finished decisively at the net.

Cilic broke the Argentine back, but Monaco found another gear as he regained his break of serve and comfortably served out for a straight-sets win.