Real Madrid had a busy summer transfer window in 2014, and while James Rodriguez and Angel Di Maria took all of the headlines, the success of Los Blancos' business will ultimately come down to the performances of Toni Kroos.
The German international swapped places with Xabi Alonso during the summer, with the latter completing a surprise move to Bayern Munich to cap off a wild window for Real.
Golden boy Rodriguez became the team's marquee signing, at the cost of losing Di Maria, who had been instrumental in the club's run to the Decima. Keylor Navas arrived, but his presence forced Diego Lopez out of the door.
Both players figure to have big futures in the Spanish capital, but neither will be as vital to the team's success as Kroos. The former Bavarian is tasked with replacing a legend in Alonso, and unlike his fellow new arrivals, he'll have to do it with limited support.
Rodriguez can struggle—Los Blancos have the offensive firepower to make up for a couple of bad performances. Iker Casillas will battle Navas for the starting position all season—the veteran has the ability to keep the Costa Rican on the bench for the foreseeable future.
Kroos' closest competition is Sami Khedira, and if the past two months are any indication, he'll be gone by the summer of 2015. Asier Illarramendi? He'll be lucky to see the pitch in cup duty and matches against lower-table sides, and Carlo Ancelotti won't feel comfortable with the youngster carrying the load in top matches.
The issue isn't whether Kroos is a better player than Alonso—at this stage of both players' careers, he is. He's younger, supremely talented and a world-class option every team in the world would kill for.
But he doesn't have the defensive presence Alonso brings to a team. Not yet. He'll have to learn to become that player, the complete midfielder Alonso had always been for Los Blancos.
The midfield is a more delicate matter perhaps, given that importance of equilibrium to Carlo Ancelotti's vision for his Real Madrid side. Two fundamental parts of the midfield from last season are gone in Angel Di Maria and Xabi Alonso, yet in James Rodriguez and Toni Kroos, Los Blancos have purchased younger, talented versions who will become integral parts of this Real Madrid side for many years to come.
However it will take time. Kroos is adapting to the position Alonso occupied with such great effect, in between the centre back, picking up the ball and acting in effect as a quarter back, distributing play while at the same providing defensive cover to the back four.
Kroos has the passing ability that made Alonso such a great fit for Ancelotti's vision. Former England striker Gary Lineker was so impressed with the way he handled the ball against the Basques, he had to make a mention of the one time things went wrong:
He'll spend most of his time on the pitch flanked by Luka Modric, and the Croatian was wildly successful playing alongside Alonso. Communication between the two appeared to be issue on Sunday, but it won't be Modric who will be asked to change his role.
It will be up to Kroos to reinvent himself as a player. If he succeeds, Los Blancos have the potential to repeat as Champions League winners and become the kind of football dynasty Florentino Perez envisions.
If he doesn't, however, and Real fail to collect significant silverware in the next two years, fans and pundits will point to the summer of 2014. They'll look at the departures of Di Maria and Alonso and identify that moment as where things went wrong.
Real are vulnerable in the centre of the pitch right now, and looking at the bench, there aren't any magical solutions to fix those issues. Kroos is the answer, and for all of the attention Rodriguez received when he arrived in the Spanish capital, it's the German who holds the keys to success for Los Blancos.