Schlager has some really good variety in his serves, but if look at Ma Lin's serves and games during 2002-2004, I think they were a lot better. Back then with speed glue, and the fact that he was just faster, and younger, his game revolved around the short game and 3 ball attack a lot more. Even if he didn't win the point immediately off the serve, it was his serve that really set up the short game, and set up his ability to execute the third ball attack. During that period, even against top players like Boll and Samsonov, he was ending the points within the first 4-5 hits, and the points never lasted very long. I remember watching a match in 2004 with him against Boll, and he won either 11-0 or 11-1 because his third ball attack game was so good.
Now that he is older he has had to rely more on his rpb and longer points, but his forehand, short game, and serve are still so good that he beats all non-Chinese players always. I don't even really remember when was the last time he lost to a non-Chinese player in a serious tournament.