Barcelona wins over Osasuna
Eto'o goals came twice in seven minutes at the start of the second half to take his tally for the season to nine.
France winger Ludovic Giuly also poached a third goal near the end but it was Argentine youngster Lionel Messi and Brazilian playmaker Ronaldinho who stole the show.
Messi's pace tormented Osasuna's defenders all night while Ronaldinho had a hand in all three goals.
Barcelona moved up to fourth in the table with 13 points, two behind leaders Real Madrid and second-placed Osasuna who are level on 15.
Real are at home to Valencia on Sunday.
Earlier on Saturday, goals from Adriano and Enzo Maresca steered Sevilla to a 2-0 home win over struggling Alaves.
Osasuna, who had not conceded a goal in three outings, made life hard for Barcelona early on.
Messi headed the home side's best first-half chance against the bar after 26 minutes but Barca found another gear at the start of the second.
Straight from the restart Messi set off on a blistering run at the heart of Osasuna's defence and rounded the keeper, only to see his shot turned wide for a corner.
Ronaldinho then set up the opener for Eto'o, who was left completely unmarked to head the ball in.
Ricardo could only push out Silvinho's cross and Eto'o stabbed home the loose ball.
The third came from a fortuitous deflection as a harmless centre rebounded off Ronaldinho's back, allowing Giuly to nip in and poke the ball into the net.
But the victory came at a cost for coach Frank Rijkaard as Brazilian defender Juliano Belletti and Portugal midfielder Deco were injured.
Belletti left the field with his knee bandaged after 19 minutes while Deco limped off in the 37th.