heart of the order (1913)

“His other high run was in strike-outs, mowing down as he did Johnson, Stovall, and Pratt in the fourth round and nailing thereby the very heart of the Browns’ batting order for the moment.” “Smoky Joe Wood Performs Well, His Hit in the 12th a Winner,” Fall River Globe, June 17, 1913, p6

No earliest use given in 2009 Dickson Baseball Dictionary