On a Friday night of carnage, the Giants had to deal with young forward Max Gruzewski and dynamo teammate Brent Daniels suffering possible season-ending injuries in a horror minute during the second quarter.
Cruising early in the third quarter when they led by 43 points, Hawthorn fought off a spirited comeback by GWS to win 14.12 (96) to 12.10 (82).
The Hawks' 10th win of the season was set-up by Watson, who kicked three goals in a memorable 10-minute burst in the second quarter.
In a halftime interview following his super spell, Watson revealed he had been dealing with a tight hamstring all week and was in doubt to play.
The 21-year-old didn't return to the field after that and spent the rest of the night sitting on the bench in a tracksuit.
While the severity of Watson's injury is unknown, the Giants added two more names to an already lengthy injury list.
GWS could be without Gruzewski and Daniels for the rest of the season after the pair went down in the second quarter.
Gruzewski, who was only returning on Friday after recovering from a hand injury, suffered a patella dislocation and was in agony as he was helped from the field.
The 21-year-old has already suffered a knee dislocation, going down in his first pre-season after being drafted in 2022.
Gruzewski is out-of-contract at season's end and is thought to be a long-term replacement for veteran forward Jesse Hogan, whose future is unclear due to ongoing injuries of his own.
Daniels, who played just five games last year due to an abdominal injury, limped off with a calf concern just before Gruzewski suffered his latest misfortune.
The forward who can do damage with cameos in the midfield, was distressed sitting on the bench with ice on his calf.
Key players Tom Green, Josh Kelly, Jack Buckley, Darcy Jones and Hogan are already sidelined, with 15 names on GWS' injury list.
Despite putting up a record third-quarter score in an onslaught of reigning premiers Brisbane last month, the Giants are facing an uphill battle to qualify for the wildcard round with a 6-9 record.
Hawthorn battered them in clearances 54-29, despite the Giants still having Clayton Oliver, Finn Callaghan and Toby Greene in the midfield mix.
Jai Newcombe, Will Day and emerging young gun Cam McKenzie were excellent to give Hawthorn's forwards space to rack up a winning score, with Jack Ginnivan also impressing.
The Hawks (10-1-4) sit third ahead of a clash with Melbourne in Launceston next Saturday.
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