Waldron did not throw his scheduled bullpen session Saturday due to a setback with his shoulder, Jenifer Langosch of MLB.com reports.
Waldron joined the Cardinals organization last season, making 46 appearances at Triple-A Memphis and finishing the season with a 4.74 ERA and a mere 4.7 K/9 mark. He has apparently aggravated a shoulder injury and will miss at least Saturday's bullpen session. As a non-roster invitee, setbacks such as Saturday's could hurt his chances at sticking in the Cardinals' major league camp.