Seeded trio Andreas Seppi, Mikhail Youzhny and Viktor Troicki were all taken the distance before overcoming scares to reach the second round of the ATP Zagreb Indoors on Tuesday.
Russian Youzhny has previous in the Croatian capital having won the 2012 tournament, but he had to dig deep to see off Blaz Kavcic 6-3 1-6 6-4.
The seventh seed broke at the first opportunity in the second game, but lost that advantage when serving at 4-2.
Youzhny recovered to break straight back and served out for the first set, only to endure a lapse of concentration in the second that saw him lose five straight games.
Kavcic wasted a golden opportunity in the decider when he failed to hold at 4-3 up, and the error proved costly as Youzhny fought back and closed out the match with his fifth break.
Earlier in the day, sevnth seed Troicki was involved in a marathon encounter with Illya Marchenko that lasted over two and a half hours - the Serbian eventually triumphing 4-6 7-6 (7-3) 7-6 (7-3).
Troicki, a semi-finalist in 2009, fired down an impressive 17 aces throughout and improves to an 8-1 record for 2015, including his triumph at the Sydney International last month.
It was a similar story for fifth-seeded Seppi, who suffered a second-set blip in his 6-2 3-6 6-4 beating of Robin Haase.
In other matches, Go Soeda saw off the challenge of Matthias Bachinger 7-6 (7-4) 7-5, while Damir Dzumhur and 2007 champion Marcos Baghdatis both needed three sets to get past Michael Berrer and Toni Androic respectively.