The U.K.'s departure from the European Union is among the top concerns for the euro area going into 2018, the incoming Eurogroup chief told CNBC.

"Brexit is a challenge and it's a challenge that is a negative shock certainly for all these economies," Mario Centeno, the incoming Eurogroup president told CNBC exclusively Wednesday. The Eurogroup is the meeting of finance ministers from the 19 countries that share the euro.

When asked about potential risks for the euro zone in the new year, Centeno said that "certainly we need to follow up on the Brexit process that I expect to be understood as a structural reform." He added that politicians in the region need to give time for economies to adapt to these structural changes.

Though the U.K. voted to leave the European Union in the June of 2016, the process is far from over with the terms of its departure yet to be finalized. As a result, the economic shocks that can eventually come from that are still not fully known.