The 34-year-old was probably feeling the effects of his 3hr 45min first-round epic against Frances Tiafoe.
This match was similarly tight but Murray lost the big points this time, with No 2 seed Schwartzman winning 6-4, 7-6 in the pair’s first meeting.
The diminutive Argentine, 29, saluted Murray after the match, saying: ‘When I grew up playing tennis, I was watching Andy, Roger and Rafa, so I have huge respect for him as an opponent.
‘I said to him it was a pleasure to play against him. We had not played before and he is coming back from an injury and every week he is playing better and moving better. I really enjoyed the match against him.’
Murray raced into a 4-1 lead but lost five games on the spin to lose the first set.
He recovered from a break down to force a tiebreak in the second, but the consistent and fleet-footed Schwartzman edged it 8-6.
For Murray, another decent opportunity to get his ranking moving in the right direction has gone by the wayside. He remains outside the top 150.Internet Explorer Channel Network