Leylah Fernandez battled past Elena Rybakina 3-6 7-6(3) 6-4 to reach the third round in Cincinnati.
The former US Open finalist saved two match points against the Grand Slam champion as she edged out a tight three set win.
It was a cagey start from both players as four breaks of serve started the match.
However Rybakina seized control towards the end of the set as the Kazakh played some flawless and aggressive tennis to win three games in a row and take the opening set in 49 minutes.
The second set saw Fernandez increase her level as she broke for a 3-1 lead before Rybakina struck back.
Fernandez worked hard on return, putting Rybakina in uncomfortable positions with the Canadian breaking for a 5-3 lead.
In important moments, Fernandez struggled to maintain her level as she was broken back with Rybakina serving for the match at 6-5.
The world number four was heading towards victory and had two match points when serving for the match but Rybakina failed to close out the win.
Fernandez capitalized and turned that moment into a momentum swing as she broke back and cruised to the tiebreak 7-3.
In the final set Fernandez put severe pressure on Rybakina and on her fourth break point opportunity, the Canadian broke serve to take a 4-3 lead.
The world number 27 would close out the win to love to set up a third round meeting with Diana Schnaider.
Meanwhile lucky loser Elina Avanesyan’s dream run continued as she backed up her win over Bianca Andreescu with victory over eighth seed Jelena Ostapenko to reach the third round.
Avanesyan will now play either Liudmila Samsonova or Magda Linette in the last 16.
