I don't see Real Madrid losing four matches in the league. Real Madrid's 8-point lead over Barcelona is enough for Real Madrid to win the matches that would make them win the La Liga title without battling with Barcelona over who will win the La Liga title this season. The match between Real Madrid and Athletic Bilbao will be a tough match for Real Madrid because Bibao wants points to remain in the fourth position of the La Liga table. Real Madrid will use home advantage to dominate and win Athletic Bilbao.
Real Madrid are in a really good shape and again they are busy counting down of matches to lift the trophy, 8 points difference is also a huge gap between them and Barcelona, with the current performance of each club i will advise Barcelona to be patient and try harder next season, talking of Athletic Bilbao I quiet agree with you that this match will be tough because ATLÉTICO MADRID are in the neck Athletic Bilbao for that fourth place, i will only say both ATLÉTICO MADRID and Athletic Bilbao are going to be fighting for the fourth place, the two matches will be very tough, which i see hope for ATLÉTICO MADRID for taking the fourth place because I don't think Athletic Bilbao can defeat Real Madrid at Madrid home, it's possible that ATLÉTICO MADRID can defeat Villarreal but still let with and see who win, the two matches are very hard to predict.
There are still many matches that will be played until the end of the season and thus, if for example Bilbao loses by Real Madrid and Atletico manages to beat Villarreal and that will make Atletico return to fourth place overtaking Bilbao. But, if in the next matches Atletico get bad results again then of course Bilbao will again overtake Atletico because after all, this season Bilbao really has a good performance compared to previous seasons. Therefore, because this season Bilbao has a good trend, then I personally believe that Bilbao will manage to finish in the top four. Also, although Bilbao will play away against Real Madrid later, but I am still very confident that Bilbao will not be defeated by Real Madrid at the Santiago Bernabeu.
Athletico Madrid just needs to do one thing to overtake Athletic Bilbao in the fourth position in the La Liga table, which is beating Villarreal. If Athletico Madrid beats Villarreal, they will gain their position back because Athletic Bilbao cannot win against Real Madrid in Santiago Bernabeu. This could be the only opportunity Athletico Madrid can get to overtake Athletic Bilbao in the La Liga table this season.