I don't think that ancelotti will play the main players in that match, now there is nothing else ancelotti is looking for in the league because indeed they have secured the La Liga trophy this season, winning or losing in that match is no longer a problem for madrid so I think they will not try to field their main players even in the first half, now ancelotti and madrid have bigger targets than just winning the rest of the league games and ancelotti will certainly save their main players to meet that big target.
For Ancelotti only strategize for a warm-up before approaching the Champions Final, because Real Madrid are guaranteed to win La Liga this year but Real Madrid will plan strategic opportunities in the match against Real Betis because some of these strategies will be useful in the Champions Final match against Liverpool.
Therefore, it looks like Betis will be able to take advantage of the situation. Considering Betis may be eyeing for a win but indeed, even though they are only three points away from Sevilla it looks like Sevilla will not lose in the last match. Sevilla only need a draw to be able to secure fourth place, of course it is still an easy job for Sevilla too. However, Real Madrid will certainly prepare well for the Champions League final, they don't need to play at full strength for their last match in La Liga.
I don't know if Carlo Ancelotti will field his best player against Betis. Because when playing at home to Real Madrid, they usually want to win,
because they don't want to disappoint their supporters. Like when facing Levante, Real Madrid fielded their best players and managed to win big.
Even though Real Madrid doesn't need a win anymore, because it has been confirmed to be the winner of the La Liga trophy.
Therefore I think there is a possibility that Ancelotti will field the best squad that Real Madrid have against Betis. Because the match will be played
at Real Madrid home, but if Ancelotti do that the risk is quite high, because there is a possibility that Real Madrid's main players are injured.
Even though the schedule for the Champions League final is only a few days away. Moreover, Betis want to win to be able to have the same points
with Sevilla, because it is still possible for Betis to shift Sevilla's position if Sevilla loses against Bilbao. So Betis will play hard against Real Madrid,
and that could make Real Madrid players more likely to get injured. I hope that Ancelotti is really focused on the Champions League final,
by not starting with their main players, in order to avoid injury. Even if Real Madrid loses, I believe the Real Madrid fans will understand and will not
blame Ancelotti. Because there is a much more important match waiting for Real Madrid, namely the match against Liverpool in the Champions League
final that must be won by Real Madrid.