Buse and Altmaier traded breaks for 3-2 and 3-3, then held serve through a tiebreak won by Buse after 64 minutes of relentless baseline tennis.
Altmaier broke for 4-2 but Buse broke back for 4-5 and again for 6-5, clinching the set 7-5 with a hold for 7-5 after 72 minutes.