I've been asked the question a couple times in my chats and promised readers I would follow up. So I asked our cracked research staff: Has a team made the playoffs with rookies starting at shortstop and catcher?
The answer, with the help of the Elias Sports Bureau: No team has made the playoffs with rookie starters at those two positions.
The closest team that meets the criteria was the 1969 Atlanta Braves. Rookie Bob Didier was the team's regular catcher, a 20-year-old who started 108 games and hit .256 with zero home runs. Sonny Jackson was the team's regular shortstop but I'm guessng suffered some sort of injury on July 13, was out until Aug. 20, came back and then went down again in mid-September. That allowed a 28-year-old minor league veteran named Gil Garrido to start 74 games at shortstop. But he only accumulated 251 plate appearances (he hit .220 with zero home runs) and Jackson still had more playing time.
Does this mean the Reds won't make the playoffs? No. Every year in baseball something that has never been done before gets done. Working in the Reds' favor is their two rookies appear to be fairly polished players. Mesoraco spent all of 2011 in Triple-A, hitting .289/.371/.484. Cozart has spent the past two years in Triple-A, hitting .310 when he was recalled to Cincinnati last July. He played 11 games and then injured his non-throwing elbow (he had Tommy John surgery). Both should be able to put up respectable numbers for their positions.
In fact, you can argue that the biggest question marks in the Reds' lineup aren't the two rookies, but the health and production of third baseman Scott Rolen and what kind of production they'll get from Chris Heisey and Ryan Ludwick in left field. Still, rookies are rookies and the Reds do need both of them to produce. Ryan Hanigan is a good backup behind the plate but Paul Janish is not an acceptable major league hitter for a team that wants to win a division title.