The midfielder found the net in the 1-1 draw at McDiarmid Park on Tuesday night with a shot from 25 yards which went in off the underside of the bar.
Whiteman only scored once for the Lilywhites in the second half of last season after a £1.6m January move from Doncaster Rovers. He had scored eight for Donny earlier in the campaign and 25 overall in his time there.
Finding that scoring form in the division above is something the 25-year-old is eager to do this season.
Whiteman said: “I was disappointed at the back end of last season that I didn’t score more goals.
“Hopefully this one against St Johnstone can kick me on. It was only a friendly but I was pleased to see the ball hit the back of the net.”
Whiteman was skipper at St Johnstone, playing an hour of the clash before Frankie McAvoy made seven substitutions.
The focus now turns to the friendly at Celtic on Saturday teatime (5.30pm).
North End’s squad are based at St Andrew’s this week and the Celtic Park contest will round off their time in Scotland.
Said Whiteman: “Celtic are a fantastic football club and we are relishing playing at their stadium.
“Hopefully we can be that bit more sharp than we were at St Johnstone.
“We’ve got another couple of days of training before then, a chance to get more work into the legs.
“Staying in St Andrew’s this week has been fantastic.
“It’s a bit out of the way and it took us quite a while to drive up last Sunday.
“The hotel staff have been brilliant with us, we’ve been well looked after.”
On North End’s return from Scotland, they have a Manchester double on the horizon.
Earlier in the week, it was announced PNE were hosting Manchester United at Deepdale on July 31.
Now they have arranged a friendly against Manchester City, with a bit of a difference.
The friendly on Tuesday, July 27, is being played at City’s Academy Stadium which is on the same site as the Etihad Stadium.
Work on relaying the turf at the Etihad is the reason why it is not being played there.
Meanwhile, North End director Peter Ridsdale has been elected on to EFL board as a Championship representative.
He has been joined by Middlesbrough chief executive Neil Bausor and Nottingham Forest chairman Nicholas Randall.
Ridsdale topped the voting in the poll, getting 19 votes from 24 clubs.