Wellingham damaged ankle ligaments when he landed awkwardly bouncing on a trampoline two weeks ago, and is still wearing a moon boot.
Speaking at the Eagles' season launch on Wednesday morning, the former Collingwood midfielder said he was "really disappointed that I'm going to miss the first couple of weeks of the season".
Coach John Worsfold said Wellingham had met with his surgeon at the weekend and elected to stay in the moon boot, pushing back his anticipated debut with the Eagles.
"It's not the normal sprained ankle," Worsfold said.
"The surgeon saw him on the weekend at our game and elected to leave the boot on for a longer period. So straight away that's making it pretty tough.
"It means he won't have to put any weight on that leg for about three weeks, so you'd expect it would take another three weeks or so to really get him up and going back ready to play.
"That, I would guess, would take round one and maybe round two out of the equation. But it's hard to predict from here about what his program will be."
Wellingham was impressive in round one of the NAB Cup, but he has since been sidelined, missing an opportunity to carve out a role in West Coast's deep midfield.
Worsfold said the 24-year-old was hurting because of the circumstances of his injury.
"I suppose you hurt if you get injured on the field [and] you're always disappointed to know you're going to miss games," he said.
"Can that be magnified if it's something that's happened off the field? I'm sure there's a fair bit of regret around, it didn't happen as part of the high-risk sport that I play."
First-year midfielder Adam Carter is also on crutches and will be unavailable for the start of the season after suffering a minor ankle sprain.
Worsfold said defender Adam Selwood would return from an arm infection against Port Adelaide on Saturday night in Alice Springs, while All Australian Beau Waters was in the mix to play his first NAB Cup game after hip surgery.
Andrew Embley, who suffered a minor right hamstring injury against Collingwood last Sunday, will continue his recovery with a view to being available for the round one Derby on March 23.
"It's not a bad hamstring," Worsfold said.
"Taking into account that he's a little bit older, we always give them a little bit more leeway.
"We certainly won't rush him, but with this sort of hamstring I think he would be available to play next week if we had a game."
Star forward Mark LeCras will play against the Power on Saturday night after making a strong return from a knee reconstruction in the first two rounds of the NAB Cup.
Forward Mark Nicoski, however, is not ready to return after missing the entire 2012 season with a severe hamstring injury.
"He's had a couple of minor setbacks in terms of just pulling back his training load," Worsfold said.
"But he could be back in full training next week and ready to play next week. He's not far away from actually being ready to play.
"What we need is for him to be able to get through two weeks non-stop."
Sharrod Wellingham is a midfielder/forward in NAB AFL Fantasy. He averaged 82.35 points in 2012. Register your team at our AFL Fantasy Hub.
Nathan Schmook is a reporter for AFL Media. Follow him on Twitter: @AFL_Nathan
