Borna Coric outlasted Marcel Granollers in an epic three-set encounter to reach round two of the Chennai Open, while Ante Pavic upset Nicolas Almagro on Monday.
Eighth seed Coric needed over two and a half hours to see off Granollers 7-6 (7-5) 2-6 6-4 at the SDAT Tennis Stadium.
There were five breaks of serve in a tight encounter, but it was Coric who made the ultimately crucial breakthrough in the third game of the decider - the Croat going on to serve out at 5-4 on his fourth match point.
Coric's compatriot Pavic is also through to round two after coming from behind to defeat Almagro 3-6 7-5 7-6 (7-1) despite being ranked 376 places below the Spaniard.
Rounding off the action, John Millman also recovered from losing the first set to beat Evgeny Donskoy 6-7 (5-7) 6-4 7-6 (8-6).