Functional deep sat midfielder that inspires confidence in the defence because reading (his own defences) frailties and making himself available for the easiest ball and then a solid range of passing. It's a chain thing. A chain is only as strong as its weakest link, and being such a solid all rounder in his own half of the pitch covered a lot of deficiencies in more specialised players around him. Lahm was converted to midfield, his knowledge of defence and his appreciation for pressure points makes him ideal to do the cover work and boss a few others about.
Although different players, Alonso in terms of on field influence for me is a poor mans Roy Keane. Only in that leading by example, doing the full 90, and being very functional in the departments required. (Keane and Alonso were/are required in differing places, but Alonso never had Paul Scholes to give the ball easy to and watch it move from there etc)
Good player, shame he played for them, hilarious he left and they were as gutted as they were. World Cup winner.