Andre Schuerrle was once again an inspiration for Mainz as a second half substitute...
Chances on goal came at a premium in the first half, but the impressive Lewis Holtby starred for Mainz, having a legitimate penalty claim turned down, testing goalkeeper Tim Wiese on one occasion and punctuating a stellar run with an effort that sailed just wide of the right post.
After the break, Risse came close before Tim Borowski's shot was saved well by Christian Wetklo. Werder would rue the missed opportunity shortly thereafter as Risse raced inward from the right flank and fired a brilliant shot to the upper-left corner of goal, putting the visitors ahead.
Eight minutes later, Holtby set up Risse with a fine through ball, and the winger squared for Schuerrle, who finished well past Wiese.
Late in the game, Werder tried to mount a comeback, but were simply out of luck. Hugo Almeida had a couple decent chances and Sandro Wagner headed off the bar, but the hosts were never able to pull even one goal back.
The result leaves Mainz atop the Bundesliga table, two points clear of Hoffenheim, who drew with Kaiserslautern. Bremen slump to tenth place with just four points from as many matches, but remain within three points of all the pre-season favourites.