Injuries happen, eventually someone on this squad will have to fill SM's shoes next year, so if he is not able to perform, that person steps up and has to perform this season. I doubt DSE is not confident he can do the job, I am equally confident he can do the job.
Losing SM will not be great, but if he is having issues with mobility well his lateral defense is already an issue, someone will need to step up and run the team and play solid on the ball defense. I think DSE will be more the capable of filling any minutes that SM misses.
Understand, but the Braves are a worse team without Sam Maniscalco. DSE is one of my favorite players, and I have great expectations for him, but even if does prove capable of replacing SM's contribution (in the event that SM is unable to play-- and I'm skeptical he can replace that contribution, btw), who then replaces DSE's minutes? I've picked BU second in the MVC, and I believe they could actually win the league if things worked out right. This is far less likely if SM misses a bunch of time.