Gretchen is making a baseball metaphor. Second baseman is a difficult position with plenty of responsibility but also fraught with hardship. It's a far less glamorous position than First baseman and less important than the Third base 'hot corner'.
She's saying that despite the apparent promotion (running her own show) it was also, in many ways, a demotion. Going from second fiddle on a primetime show to presenting in a dead slot is akin to being called up to a big league baseball team but then being asked to play in this thankless (and undervalued) position.
She clearly equates 2B with failure, not success.
GRETCHEN (V.O.): Back in Minnesota, before I was famous, before I graduated summa cum laude from Stanford, before I was Miss America, I played second base in our sixth-grade softball league.
GRETCHEN (TO CAMERA): I hate second base.