The Two London teams meet at the Olympic Stadium on Wednesday night as Westham were looking to complete a league double over Chelsea since the 2003/2004 season.
Soucek thought he has scored for the hosts in the 35th minute after getting on the end of a rebound inside the box but VAR controversially ruled it out for Offside.
Willian scored a penalty to put the blues ahead but soucek equalised three minute into the first half stoppage time.
Westham took the lead in second half after Antonio scored but Willian scored a beautiful freekick in the 72th minute to equalise.
Andriy Yamolenko scored the Winner for the hammers in five-goal thriller.