Athletic Bilbao kept up their impressive run of form by beating Real Betis 3-1 at San Mames to stay in the fight for the fourth Champions League place in the Primera Division.Sabin Merino scored either side of half-time to compensate for the absence of top scorer Aritz Aduriz, who started on the bench.Mikel Rico also netted for the Basques and Ruben Castro got a late consolation goal for Betis.Ernesto Valverde's side stay sixth in the table but Sevilla's win over Villarreal means Athletic are just six points behind the Yellow Submarine, who occupy fourth spot, and a single point behind Sevilla.Athletic pressed their opponents relentlessly in the first half but did not get their rewards until the 34th minute.Mikel San Jose chipped a delightful pass into the area and Merino brought it down with his chest and onto his right foot, slamming past Antonio Adan from close range.The Basques were intent on getting another before the break and appealed for a handball as Francisco Molinero blocked a header from Iker Muniain, but while players from both sides waited to see the reaction of the referee, Rico played to the whistle and smashed the loose ball in at the near post.Rico looked for a second goal early in the second half by hitting another loose ball at Adan following a corner, and Merino was on hand to score from the rebound as the goalkeeper repelled the midfielder's shot.Betis were not completely out of the game and Castro headed home from a corner just a minute after hitting the far post, but there was barely any time left to continue their comeback bid.