Jay made his big league debut for the Cardinals in 2010, after batting .301, with 34 home runs (HR), an .803 on-base plus slugging percentage (OBP), and 61 stolen bases (SB), in 409 minor league games. The starting center fielder for four consecutive National League Championship Series (NLCS)-qualifying clubs as a Cardinal (2011−14), he was a World Series champion in 2011, as the Cardinals defeated the Texas Rangers. Between 2011 and 2013, Jay established an errorless record streak for National League (NL) center fielders at 245 games. In 2012, he finished tenth in the NL in both batting average and on-base percentage (OBP).