The World Series Champion Chicago Cubs just lost a key player to their championship title run. The Cubs’ free-agent center fielder agreed to a deal with the rival St. Louis Cardinals on Thursday, according to ESPN’s Mark Saxon.

St. Louis has scheduled an 11 a.m. ET news conference Friday. The Cardinals and Cubs open the 2017 MLB season on April 2 in St. Louis in a game that will now have an extra layer of intrigue.

Terms of Fowler’s deal with St. Louis were not immediately known or reported.