Thousands of Valencia fans protested against owner Peter Lim and the reported detention of two fans in Lim's home country of Singapore before and after its 3-2 loss to Las Palmas in LaLiga on Monday.
Dani Cuesta and his wife were detained in Singapore almost three weeks ago after Cuesta reportedly held up anti-Lim signs.
Valencia fans have been protesting Lim's management of their club for years.
The millionaire businessman bought Valencia in 2014 but supporters have been angered by what they feel is his absentee ownership, and thousands rallied outside Mestalla Stadium before the game.
Thousands more returned after a defeat that left Valencia bottom of La Liga with just one win in 10 matches.
The game started well for the home side with Pepelu putting Valencia ahead from the penalty spot after 14 minutes.
But Alex Muñoz equalized for Las Palmas three minutes before halftime and on-loan Wolverhampton Wanderers striker Fábio Silva put it 2-1 ahead seven minutes into the second period.
Pepelu was sent off for an off-the-ball incident after 69 minutes and Alberto Moleiro added a third for Las Palmas soon after.
César Tárrega got a goal back in stoppage time for Valencia but it was too little too late and Las Palmas celebrated a surprise first win this season and its first in La Liga since February.
The victory lifted it above Valencia on goal difference and off the bottom of the table.