FC Barcelona can clinch La Liga if they win against Deportivo Alavés tomorrow and Atlético Madrid lose against Valencia the next day. Five matches are left in the season, with Barcelona currently on 77 points and Atléti on 68. If these two results go as Barcelona hope, then they will be on 80 with the Madrid team on 68.
Four matches would be left, so even if Barça lose out and Atlético win out, Barcelona would have 80 and Atléti would reach 80 as well. However, Barça would still win the title based on the fact that they own the tiebreaker, which is head-to-head goal difference.
Atlético drawing would be a positive development for the Catalans, but the league title would not be assured yet. Atléti would reach 69, and Barcelona could reach 80 with a win. Any additional draw or win by Barcelona, or draw or loss by Atléti would give the blaugrana the title.
If Barcelona and Atlético have the same result in the next round (both win, both lose, or both draw), the league title is assured if either Barcelona win, Atlético lose, or both teams draw at any point in the next four matches. One last possibility exists for Barcelona to win the league: to draw at least three of the next four matches. This is functionally the same as winning one game as they would gain 3 points. Even if Atléti win all four of their matches, Barça win through their tiebreaker.
Meaning that at no matter what, if Barcelona win two matches or Atlético lose two of any of the five matches each team has left, the Catalans will win La Liga again. There is also the alternative for Barcça to win one match and draw three others, as with 6 points, Barcelona would have enough to assure the title.