Diaz is likely to see some starts at the shortstop position while Jhonny Peralta is out with a hand injury.
The Cardinals originally planned on having Jedd Gyorko face lefties in a platoon with Kolten Wong at second base. However, with Peralta now out 2-to-3 months, Gyorko will take over as the everyday shortstop and Diaz will receive most of the starts against left-handed pitching. The 25-year-old will hit near the bottom of the lineup when he starts and has no major league experience, making it questionable how valuable he can be for fantasy owners.