Ancelloti has won almost every major trophy during his time as a coach and maybe a season without a trophy is not a big deal for his reputation. La Liga still has a chance that they can chase as long as they can make a much better performance because when they face El Clasico they can close the gap on Barcelona even though they will still be one point behind Barcelona.
Ancelotti is a ledgendary head coach and he has gotten many big titles in his coach career from AC Milan, Real Madrid, Chelsea, Bayern Munich and PSG. Don't forget that Ancelotti is a coach that helped Real Madrid achieving the "Decima" in UEFA Champions League after about one decade of waiting and trying with many coaches including Jose Mourinho.
They won the Decima (10th Champions League title) in 2014 after 12 waiting years since the 9th title in 2001–2002 season with a magic volley goal from Zidane to beat Bayer Leverkusen of Michael Ballack.
Anyway, in general the head coach position in Real Madrid is high pressure and one failed season means you have to go, and with Ancelotti it is this season.
Barcelona will be more focused on preparing for the semi-finals in the Champions League so the coach will definitely make some rotations and if the results are beyond expectations because they will draw in the next match then this scenario can be used well by Real Madrid so they can chase points in the crucial match when the two meet.
Barcelona have amazing chances of winning 4 titles in this season but they have yet won any title now. Coming matches will decide how many titles Barcelona actually win in this season or whether they finish the season with empty hands, no single title, it will be a nightmare unimaginabe ending for them.