Well Sheahan doesn't provide any scoring. The only thing keeping him in the lineup is that he's a centre. Inserting Jurco for Sheahan would take a lot of line juggling but I think Sheahan is the most deserving of being scratched if we're trying to insert a scoring third liner onto the team
So, Sheahan scored more than Jurco in 2013-14. Sheahan scored more than Jurco in 2014-15. Sheahan has admittedly dropped off in scoring so far in 2015-16, but still has as many goals in 21 games as Jurco had in 63 games last season. And, as you mention, outside of scoring Sheahan is the more useful of the two when in the lineup because he can play center. But, Sheahan should be removed from the lineup and replaced with Jurco.... for more scoring?