VfB Stuttgart’s early season struggles continued on Saturday in the Bundesliga when last season’s runners-up had to swallow a stoppage-time 3-3 against Mainz after wasting a two-goal lead. Stuttgart led 2-0 after 15 minutes from Enzo Millot and Jamie Leweling but a penalty from Nadiem Amiri and Jonathan Burkardt’s in the 62nd put Mainz level. Fabian Rieder’s 88th-minute free-kick, which hit the post but went in off goalkeeper Robin Zentner, seemed to have won it after all the hosts. But Mainz hit back again four minutes into stoppage time from Maxim Leitsch. It was the third time in four seaso…