Not sure what Fnord's getting at:

The worst headup hand is 23, but of course you can win with it. Anyone want to rephrase?

9 high win doesn't seem possible

1: 23
2: 24

Board would have to be
5689T
or
5789T
in order not to have a pair or straight

A nine high split could happen
1:23
2:23

B: 45789