▁the ▁ 2 0 0 7 ▁season , ▁Baseball ▁America ▁r ated ▁him ▁No . ▁ 7 4 ▁on ▁their ▁list ▁of ▁Top ▁ 1 0 0 ▁prospect s , ▁and ▁No . ▁ 3 ▁in ▁the ▁Pir ates ' ▁organization , ▁behind ▁Andrew ▁McC ut chen ▁and ▁Brad ▁Lincoln . ▁ ▁In ▁ 2 0 0 7 , ▁the ▁Pir ates ▁invited ▁Walker ▁to ▁spring ▁training ▁as ▁a ▁non - ro ster ▁player , ▁where ▁he ▁was ▁converted ▁from ▁his ▁draft ed ▁position ▁of ▁catch er ▁to ▁third ▁bas eman . ▁He ▁was ▁sent ▁back ▁to ▁the ▁Pir ates ▁Double - A ▁affili ate ▁Al to ona ▁Cur ve ▁where ▁he ▁spent ▁the ▁majority ▁of ▁the ▁season . ▁On ▁May ▁ 1 5 , ▁ 2 0 0 7 , ▁he ▁became ▁the ▁first ▁Cur ve ▁player ▁to ▁have ▁a ▁four - hit ▁game , ▁going ▁ 4 - for - 4 ▁with ▁a ▁home ▁run , ▁double ▁and ▁two ▁R BI ▁against ▁the ▁Port land ▁Sea ▁D ogs . ▁Walker ▁hit ▁a ▁pair ▁of ▁two - run ▁home ▁runs ▁on ▁May ▁ 2 7 , ▁ 2 0 0 7 , ▁helping ▁the ▁Cur ve ▁end ▁a ▁ 1 0 - game ▁losing ▁stre ak ▁against ▁the ▁B owie ▁Bay so x . ▁He ▁hit ▁a ▁grand ▁sl am ▁and ▁drove ▁in ▁five ▁runs ▁on ▁June ▁ 2 8 , ▁ 2 0 0 7 ▁in ▁the ▁second ▁game ▁of ▁a ▁double - header ▁against ▁the ▁Tr ent on ▁Th under