The World No. 17 recovered from a 3-5 deficit in the third set, winning the final four games to take a 6-3, 3-6, 7-5 victory.
All three of Schwatzman’s match points came in the tenth game of the final set, but three untimely unforced errors from the eighth seed kept the match alive.
Bautista Agut required two match points of his own to win the match, ultimately taking the dramatic third set after a Schwartzman backhand went long. The Spaniard now owns a 2-1 ATP Head2Head lead over Schwartzman, having beaten the Argentine in the same event in 2019.
Bautista Agut is chasing his first ATP Tour title of the season, having reached the final in both Dubai and Montpellier in 2021. Coming into Toronto the 33-year-old was on a three-match winless run, but has turned his fortunes around this week with impressive victories over Schwartzman and American Tommy Paul.
Bautista Agut has now reached nine ATP Masters 1000 quarter-finals in his career. It is also the third time that he has reached this stage at the National Bank Open Presented by Rogers, appearing in the quarter-finals in Montreal in both 2017 and 2019.