Actually from what I gather (and i did read two books Erich mentioned), there wasn't much chance of a victory in the south. The Russians gained enough time with the battle at Prokhorovka to establish new defensive positions and await the Germans. On 13th the offensive was called off but Hitler allowed Manstein to continue with operations in the south till the 17th when the forces were transferred to Mius. The Germans lost the momentum and with it the tactical victory in the south (SS-Grupf. Krüger analysis this in a document composed after the battles at Mius)

Manstein sole reserve (by this I mean Army group's sole reserve) was Nehring's 24.Pz.Korps with three under-equipped panzer division's (17., 23. and 5.SS-Pz.Gren.Div.), but this was on 15th or 16th already sent to Izyum.