In last season, Real Madrid were on good run and with this luck was also giving them good favor because Barcelona having the worst start of season and Sevilla and Atlético Madrid were not able to give them good competition, so they enjoy good wins in La Liga and Champions League but in this season as Barcelona is preparing they have to manage things in strong way because now it's not easy to do like they already achieve in last season. But, with the best combination of old and new players they are still very strong and capable of win any title which they won last season.
As many already posted there is no doubt Modric, Benzema, Vasquez are their key players for next season as well and if anyone slumps it's going to be worst for them like Barcelona.
Indeed, at this time the combination of Barcelona in the future will be more promising, plus if their finances recover from the crisis. Unfortunately, their finances are the biggest obstacle to making many breakthroughs to bring in other great players. Now Barcelona is struggling with confidence even with minimal finances, it turns out that Xavi's seriousness can be seen again bringing back the El clasico era.
Real Madrid does have a key that can last until next season, in exchange there will be alternative players who will certainly be reserved to close the gap in the future. But it must be admitted Real Madrid will be difficult to predict.