Leon Legge's first senior goal was enough to send hosts Brentford into the third round of the FA Cup at the expense of Walsall.
The big centre-back struck early on with a powerful header from John Bostock's corner to ensure a potentially money-spinning tie.
But the stopper was also the hero at the other end as he slid in with a last-gasp tackle to deny Steve Jones in the dying minutes.
Brentford were always good value for the win, Ben Strevens forcing a full-length save from Saddlers goalkeeper Clayton Ince before wasting a gilt-edged chance.
The Bees also had strong claims for a penalty turned down when Strevens' curling shot was knocked down by the hand of Mark Hughes.
Walsall, despite a late rally, rarely threatened and Brentford keeper Lewis Price was only called on in the dying minutes to make a double save from Matt Richards and Troy Deeney.
