Real Sociedad lost 2-1 away at struggling Leganés while Sevilla were held to a 1-1 draw at home to Alaves.
In between, Getafe had carved out a 2-0 victory away at Bilbao to put them in pole position behind the two title challengers, Real Madrid and Barcelona.
Jose Bordalas' team are now ahead of Sevilla on goal difference, while Real Sociedad are five points further back.
Getafe missed out on fourth on the final day of last season but they continue to prove their challenge was far from a one-off.
Their success has been built largely on a solid defence but Damian Suàrez's opening goal at San Mames came after a brilliant attacking move, as he exchanged consecutive one-twos before weaving through and finishing into the corner.