Francisco Cerundolo and Tomas Martin Etcheverry produced the biggest upset of the opening day in the National Bank Open doubles draw, knocking out defending champions Julian Cash and Lloyd Glasspool in Montreal.
The Argentine pair recovered from a second-set loss to beat the sixth seeds 6-4, 3-6, 10-7 in the Match Tie-break, ending the defending champions' title defence at the first hurdle.
Cash and Glasspool arrived in Montreal with plenty of confidence after winning the title in Washington, but they were unable to carry that momentum into their opening match. Cerundolo and Etcheverry stayed composed when it mattered most, edging the deciding tie-break to claim one of the tournament's early surprises.
Elsewhere, former singles world No. 1 Daniil Medvedev showed his versatility in doubles as he teamed up with Fabian Marozsan to defeat Canadian wildcards Liam Draxl and Cleeve Harper 4-6, 6-4, 10-6.
Top seeds Harri Heliovaara and Henry Patten enjoyed a much more straightforward start to their campaign, beating Ignacio Buse and Flavio Cobolli 6-3, 6-2 in just 64 minutes. The efficient victory underlined why the pair are among the leading contenders for the title.
The home crowd also had plenty to celebrate as Canadian wildcards Duncan Chan and Alexis Galarneau pulled off another notable upset. They defeated the experienced pairing of Marcelo Melo and Alexander Zverev 6-3, 7-6(5) to advance to the next round.
With defending champions already out and several unexpected results on the opening day, the doubles draw in Montreal has quickly opened up. The tournament now heads into its next stage with the remaining teams looking to take advantage of a field that has already produced plenty of surprises.
