Alexander Bublik's status as the Estoril Open's fifth seed meant little to Pedro Martinez as the Spaniard romped to victory.
Qualifier Martinez needed just 53 minutes to see off a player ranked 57 spots above him, triumphing 6-3 6-0 to reach the second round.
He will now face Cameron Norrie, a 6-1 6-3 winner over home hope Joao Sousa in Portugal.
Marin Cilic, himself seeded sixth, might have feared going the same way as Bublik after a chastening second set against 17-year-old Carlos Alcaraz.
But the Croatian held his nerve and got the job done in a 6-3 1-6 6-4 success.
Finally, fellow seed Albert Ramos-Vinolas was relatively untroubled in overcoming compatriot Fernando Verdasco 6-3 6-3 in an all-Spanish clash.
At the BMW Open, Jan-Lennard Struff secured safe passage to the second round on home soil in Munich.
The German saw off lucky loser Andrej Martin 6-4 6-3 and the seventh seed now face Dominik Koepfer, who downed three-time champion Philipp Kohlschreiber 4-6 6-4 6-3.
Elsewhere in the draw, Nikoloz Basilashvili, seeded fifth, defeated Thiago Monteiro, while the sixth-seeded Dusan Lajovic suffered a straight-sets loss to world number 127 Mackenzie McDonald.