The 19-year-old midfielder scored a superb solo goal against York on Saturday, the only bright spot in Pompey's 4-2 defeat.
Whittingham said: "Jed scored a good goal.
"I think he was the stand-out player for us and showed a side to his game that we hope he can take forward.
"He's maturing all the time. He's a good player and he proved that with his performance."