Fourth seed Juan Monaco was pushed all the way by Jan Hernych before progressing to the second round of the If Stockholm Open.
The Argentinian won the first set 6-2 but then lost the second 7-5 before edging the third by the same score in just under two hours 10 minutes.
Monaco served 10 double faults - compared to his Czech opponent's four - but he edged it.
However, sixth seed Benjamin Becker crashed out to fellow German Simon Greul 2-6 6-3 7-5.
The! re was a further shock when seventh seed Alberto Montanes was knocked out in straight sets by Leonardo Mayer.
Montanes had a poor all-round game against his Argentinian opponent ranked 31 places beneath him but it was Mayer who won through 6-4 6-3.
Guillermo Garcia-Lopez enjoyed a straightforward 6-3 6-2 victory over Alberto Martin in one and a quarter hours.
Joachim Johansson served 21 aces as he overcame a ranking deficit of more than 400 places to defeat Peter Luczak 7-5 6-2.
