Midfielder Wallace popped up in the penalty area with 15 minutes to go to tuck away Patrick Agyemang's low cross and secure a point for lowly Pompey against table-toppers Doncaster.
"He was supposed to be wing-back at the time, but somehow he ended up in the penalty box," said Whittingham.
"That's the asset he's got, he can run and get around the pitch.
"The ball went underneath David Connolly's foot and fell nicely for Jed. It was his best pass of the game to put the ball in the back of the net."