But the news was nowhere near as good for fellow Port key forward Jay Schulz, who was subbed out in the third quarter with a right ankle injury.
Essendon also suffered an injury to a key player, with running defender Michael Hibberd damaging a hamstring in Port's 1.11.15 (90) to 0.9.11 (65) win.
Rising Essendon key position star Joe Daniher was the dominant player on the ground in the early stages, kicking one first-quarter goal following a strong pack mark and missing two other good opportunities.
The Bombers led by 24 points after a goal from Kyle Hardingham, only to have the margin halved in a matter of seconds by Westhoff.
The rangy Power key-position player booted the Power's first goal after taking a good mark and was immediately awarded another shot from point-blank range after being dragged to the ground by Mark Baguley.
Schulz kicked two late goals to give the visitors a one-point lead at the first change.
The second quarter was a mostly forgettable affair, with Westhoff's third goal and a response from Michael Hurley the only major scores.
Daniher had six marks and a team-high 10 possessions to halftime.
After an anonymous first half on his Essendon debut, star recruit Paul Chapman worked his way into the match in the second half and finished with 24 possessions.
The highlight of the third quarter was a super goal to Port's Jared Polec.
Port got the margin out to 21 points midway through the term, although Essendon finished strongly with three of the last four majors to trail by just 10 at the final change.
But they were unable to get any closer, with the Power outscoring the Bombers three goals to one in the final term.
Former Bomber Angus Monfries ended the match by kicking a spectacular - and no doubt satisfying - goal from the boundary line after the final siren.
Both clubs selected strong teams for the Tuesday night clash.
Tall defenders Alipate Carlile and Jackson Trengove did not play for Port Adelaide, while Jake Carlisle, Courtenay Dempsey and David Myers were not selected by the Bombers.
Rival coaches Ken Hinkley and Mark Thompson were reasonably confident that Westhoff and Schulz had both escaped serious injuries.
Hinkley said the early indications were that Schulz had suffered a mid foot sprain, which he should recover from in time for Port's opening match of the home and away season against Carlton on March 16.
"Jay did the same thing last year and played through it with no problems," said Hinkley.
"Having the extra week to go before we start the season clearly we won't take a risk if we don't need to.
"As I sit here right now I'm very confident about round one, but he's got to go and see the doctor who'll scan it and see what he looks like."
Thompson said Hibberd's hamstring strain was at the very minor end of the scale, which should also allow him to return for the beginning of the regular season.
PORT ADELAIDE 0.4.3 0.5.10 1.8.12 1.11.15 (90)
ESSENDON 0.3.8 0.4.10 0.8.11 0.9.11 (65)
Nine pointers: Port Adelaide - Polec. Essendon - Nil.
Goals: Port Adelaide - Westhoff 5; Schulz 2; Monfries, Butcher, Gray. Essendon - Daniher 2; Steinberg, Goddard, Hocking, Winderlich, Hardingham, Hurley, Colyer.
Best: Port Adelaide - Polec, Westhoff, Gray, Pittard, Wines. Essendon - Zaharakis, Heppell, Daniher, Chapman.
Umpires: Ben Ryan, Heath Ryan, Andrew Talbot.
Official Crowd: 8022 at Etihad Stadium.