Wallace, 19, who has been with the club since 2011, was on the scoresheet in Pompey's 4-2 defeat to York City at the weekend.
"Jed scored a good goal. I think he was the standout player for us and showed a side to his game that we hope he can take forward," Whittingham told the club's official website.
"He's maturing all the time. He's a good player and he proved that with his performance."
Wallace has scored twice in 11 games this season.