The Reds were 1-0 up after four minutes when he quickly anticipated and intercepted a bad defensive pass, rounded the goalkeeper and slotted home.
It was 1-1 two minutes later however when Schindler headed home into an empty net after Scott Carson was beaten by the original shot that cannoned back to Schindler off the woodwork.
Riise restored the Reds' lead after fifteen minutes when he hammered home a free kick from thirty yards, although the goalkeeper should have done better with it.
Voronin impressed with his link up play with Crouch at Crewe and again in the first half, and after the break he was quickly on the same wavelength as subsitutes Dirk Kuyt and Yossi Benayoun.
Benayoun played a good ball into the box which Voronin cleverly dummied through his legs to allow it to roll to Kuyt who scored from ten yards out. Unfortunately the goal was disallowed for offside.
It was 3-1 minutes later though when Voronin ran onto a Xabi Alonso through ball before calmly slotting the ball home. That was the Ukrainian's last action as he was then replaced by Fernando Torres.
Torres quickly showed what he could do, with some clever footwork and a quick turn of pace to set up a chance for fellow debutant Ryan Babel but a Werder Bremen defender managed to turn the ball over the bar at the last moment.
Torres had a couple of chances himself, but saw one go narrowly wide and then saw the goalkeeper make a fantastic save after he'd reacted quickest to a rebound following a Dirk Kuyt belter.
The German side thought they'd pulled a goal back on 80 minutes but it was clearly offside, although it took the officials nearly five minutes, and a false restart before they disallowed it. In fairness it's pre-season for referees and their assistants as well.
Werder Bremen did make it 3-2 minutes later but the Reds held on for their third successive pre-season win.