The Australian stopper tipped over shots from Jonathan Potroipa and Trochowski before reacting well to save a stinging David Jarolim drive that came through a crowd of players.
Shaun Wright-Phillips became the first player to be yellow-carded after 29 minutes for a challenge on Jermaine Jones, but striker Miroslav Klose headed Trochowski's resulting free-kick over the bar.
There was still time for Trochowski to pick up a booking that rules him out of the second leg - a further boost to Fulham on a good evening for the west London club.