Welch, 24, is also out of contract next season and was in the sights of several sides. Instead he faces a second knee reconstruction after having one during the 2017 premiership season.
He will undergo scans in the coming days to confirm his injury but the Storm strongly suspect he has ruptured his anterior cruciate ligament.
While both sides ran up the score last game, the first 20 minutes was a cagey affair as they played for position and traded penalty goals.
On 28 minutes Papenhuyzen, who ran for 247 metres, broke up the game and the Tigers defence as he burst through two tacklers and ran 80 metres untouched to score, his finish looked like an uncompetitive heat at the Stawell Gift as he ran in for the try.
The Storm’s defence wasn’t ticking over though and the Tigers had over 60 per cent possession, finally turning it into a try on 35 minutes as Josh Aloiai was put over to score and give the Tigers a 12-8 lead at half-time.
Luke Brooks stretched out to score the first try of the second half as the Storm looked flat after the break.
But Cameron Munster put up a high ball soon after and it fell into the hands of Felise Kaufusi right next to the right post allowing him to go over and cut the lead to 16-14.
The Tigers were controlling play and possession and Marshall pulled out a genius flat pass on to Esan Marsters on 55 minutes with the winger twisting and scoring to make it 22-14.
A try to Seve gave the Storm a chance at the win with eight minutes to play trailing 22-20, then with just minutes to play Kenny Bromwich broke a tackle down the Storm’s left edge and drew in defenders before passing inside to Chambers who ran over to score.
It was unclear exactly how Welch hurt his knee. One replay appeared to show him grimace while running in support of a teammate just moments before half-time.
Welch is believed to have felt his knee go so he moved to the sideline and signalled to the Storm bench he was in trouble.
As the players walked to the sheds, teammates Nelson Asofa-Solomona and Jesse Bromwich walked back to Welch and offered to help him off. Instead, he hobbled off with them at his side.
It’s an injury the Storm couldn’t afford and neither could Welch.
The Storm play Canterbury Bulldogs at Belmore next Sunday at 2pm.
MELBOURNE 24 (W Chambers F Kaufusi R Papenhuyzen M Seve tries C Smith 4 goals) WESTS TIGERS 22 (J Aloiai L Brooks E Marsters tries E Marsters 5 goals) at AAMI Park. Referees: Gavin Badger, Adam Gee. Crowd: 11,402.
Roy Ward is a Sports writer for The Age.