We know why Chelsea needed a defensive midfielder. Our transition game has been poor, and while Ramires and Frank Lampard are both fine players, neither are naturals in the deeper role they're currently being employed in, and thanks to Marco van Ginkel's injury there's simply not enough depth to keep everyone fresh. Adding Nemanja Matic, described by the ever-annoying Jorge Jesus as 'the best defensive midfielder in the world' makes a lot of sense -- he's an upgrade on our current cast and he adds a much-needed extra body to the squad.
But there's another reason you should be excited about his arrival. Midfield reinforcement is all well and good (all well and great, in fact), but that's not the only place that Matic helps us. During the first half of the season, Chelsea have been strong on set pieces; with Wednesday's transfer they can now absolutely swamp the opposition on corners and free kicks.
Jose Mourinho could, in theory, field all of John Terry (6'1-1/2"), Gary Cahill (6'3"), Branislav Ivanovic (6'2"), John Obi Mikel (6'2"), Nemanja Matic (6'4") and Demba Ba (6'2") at once. All six are legitimate threats to score on corners and free kicks; all six are more than capable of holding their own defending them.
How, exactly, is the opposition supposed to mark that group? Most teams just won't have enough big players to cope, giving Chelsea a mis-match somewhere and giving our set-piece takers a nice target to aim for. If we need to shut up shop and play defensively, something that might happen at the Etihad or if we end up facing a very strong team in the Champions League, Matic's height gives us a potent weapon on set pieces. I guarantee that at some point we'll be celebrating it.