New York, USA, 15 February 2019 | AAP /

Australian John Millman has suffered an upset in the second round of the New York Open, losing to Guillermo Garcia-Lopez in a tight three-setter.

The world No.102 Spaniard broke the fourth seed’s serve just once on his way to a gutsy 7-6(4) 1-6 6-4 victory in two hours and 11 minutes.

It leaves Jordan Thompson as the only Australian left in the ATP 250 event after booking a quarterfinal clash with big-serving American John Isner, who beat Bernard Tomic in straight sets.

Despite the loss, it has still been an impressive start to the season for Millman, who until now had not lost an opening-round match in 2019.

He reached the second round at both the Brisbane International and the Australian Open – where he fell in five thrilling sets to Roberto Bautista Agut – and advanced to the quarterfinals of the Sydney International, where it took Gilles Simon to stop him in a third-set tiebreak.

He also won his singles rubber in Australia’s dominant performance against Bosnia & Herzegovina in the Davis Cup qualifying tie in Adelaide.