Alexander Zverev sent David Ferrer into retirement at the Madrid Open, while Juan Martin del Potro's return ended in defeat.
Zverev ended Ferrer's career with his second-round win on Wednesday as the 37-year-old 2013 French Open runner-up bid farewell to the ATP Tour.
Back after more than two months out with a knee injury, Del Potro went down to Laslo Djere at the ATP 1000 clay-court event.
But the seeds were relatively strong otherwise, with Rafael Nadal joining defending champion Zverev in easing through his second-round match.
FERRER'S CAREER ENDS WITH ZVEREV DEFEAT
A 27-time title winner on the ATP Tour, Ferrer was unable to extend his career another match.
The Spanish veteran suffered a 6-4 6-1 loss to Zverev, the third seed and last year's champion, in the second round.
"I never expected a goodbye or farewell like today," Ferrer said, via the ATP Tour website. "I tried to play at a high level during the last year, but a day like today, people at work tomorrow, everyone stays here to support me and that is something that I will only have in my mind and in my heart.
"It's something I will never forget."
DEL POTRO BOWS OUT ON RETURN
The seventh seed, Del Potro's return ended with defeat as the Argentinian was edged by Djere 6-3 2-6 7-5.
Djere has already secured the title in Rio de Janeiro this year and the Serbian made the most of his opportunities in the deciding set.
As Del Potro won more return points and squandered five break-point opportunities, and a match point, Djere took his only chance to seal victory in two hours, 22 minutes.
NADAL, WAWRINKA CRUISE ON GOOD DAY FOR SEEDS
A record five-time champion in Madrid, Nadal brushed past talented Canadian teenager Felix Auger-Aliassime 6-3 6-3.
Of the eight seeds in action, six won, with only Del Potro and Karen Khachanov – who was edged by Fernando Verdasco – departing.
Stan Wawrinka, the 2013 runner-up, is unseeded, but the Swiss star was too good for Guido Pella 6-3 6-4, setting up a last-16 showdown with Kei Nishikori.
Nishikori survived a test against qualifier Hugo Dellien before recording a 7-5 7-5 victory.
Stefanos Tsitsipas, the eighth seed, had few problems getting past Adrian Mannarino 6-2 7-5, while there were also wins for Gael Monfils and Fabio Fognini.