The rotation that misfired early in the season has collected itself and provided 51 quality starts, the sixth-most in baseball. That has helped the Cardinals to the third-best run differential in the majors, plus-89.

That stew of stats, especially the run differential, suggests that the Cardinals should have a better record, that they have the makings of the team they aim to be. Baseball Prospectus and Baseball-Reference.com calculate that the Cardinals, who sometimes feel “20 games below” .500, should be 53-35. That ties the first-place Cubs’ record. Ten of the 15 teams in the NL are within three, plus or minus, of their run differential pace.

The Cardinals are minus-7, the biggest lag in the NL.

The reasons vary, from the struggles in the bullpen to the frayed defense, the rotation’s early failings to manager Mike Matheny’s decisions. The Cardinals are 7-15 in one-run games and once lost 10 consecutive games to winning teams — at home. Trevor Rosenthal’s removal from the closer position has created upheaval elsewhere in the bullpen, and Matheny’s deployment of the relievers has left late innings untended or leads exposed. The manager has long maintained that the Cardinals have all the pieces of a contender. Matheny operates often on faith on how they should be put together.