Atletico Madrid's ability to force La Liga's title pace will be tested on Saturday when the leaders face Athletic Bilbao.
In what has become one of the most entertaining Spanish title races for some time, Diego Simeone's men now have their destiny in their own hands.
Thanks to the form of traditional heavyweights Barcelona and Real Madrid, Atletico have done much of their good work this season as part of the chasing pack.
However, after a week in which they have moved a point clear at teh top of the table, their title credentials will face a stiff test against fourth-placed Bilbao on Saturday.
Such is the nature of this season's title race that a defeat for Atletico could see them slip to third by the end of the day, while victory can put them four points clear at the top.
While Atletico have won their last four league outings without conceding a goal, Saturday's hosts have also been in impressive form as they look to have all but nailed down the final Champions League spot.
Barring a major collapse late in the season, Ernesto Valverde's side could play in the qualification rounds for next season's Champions League, an achievement that has been helped by a run of just one defeat in their last 12 league games.
Aside from defeats to Real Sociedad and Espanyol, Bilbao have proven tough to beat in 2014 and striker Diego Costa will likely have a big say in whether Simeone and company return to the capital with three points.
Costa has five goals from his last four games in all competitions and was on hand to score the winner the last time the teams met - finding the net with four minutes to go in a 2-1 Atletico victory.