With button calling he's not [censored] around as much, so it should be strong combo draw or at least NFD, which he can't have, if he doesn't have you beat. Let's do a pokerstove and give him KK as well, since this is full ring and all:
<font class="small">Code:</font><hr /><pre>Board: 9s 5h 4s
Dead:
equity win tie pots won pots tied
Hand 0: 44.899% 44.90% 00.00% 8890 0.00 { AdAs }
Hand 1: 55.101% 55.10% 00.00% 10910 0.00 { KK, 99, 55-44, 8s7s, 7s6s, 6s5s, 54s }</pre><hr />
Hm. Better than expected. Take out KK though and you're ~22%. Then again, it doesn't seem a very unreasonable line for KK. And why can't he have QQ?