The 21-year-old has been sidelined for the past month with a calf injury but was spotted shooting hoops on Monday night, having listed his name on the team sheet as "Phill Inn".

Coach Nathan Buckley says Sier will likely face disciplinary action, noting that the youngster had also lied about the incident when confronted.

Sier initially told the club he had just been watching friends play and shooting around during breaks.

"(It was) a blue from a young player," Buckley told reporters on Thursday.

"He made a couple of errors in the whole situation; one, to play the game and two, to try to sweep it under the carpet.

"We'll deal with that accordingly and appropriately but we've got a game to prepare for on Saturday, which he won't be a part of.

"Our VFL don't play this week, so we've got a bit of time to sort that out."

Sier played in last year's grand final defeat to West Coast but has struggled to hold his spot this season, managing just six games.

Buckley said he would be involved in deciding what sanction to hand down, along with football boss Geoff Walsh and the club's leadership group.

The fifth-placed Magpies travel to face Adelaide on Saturday and will again be without hamstrung stars Jordan De Goey and Darcy Moore.

De Goey is no certainty to face Essendon in next week's final round of the home-and-away season but will be given every opportunity.

"He's continuing to ramp up with his speed work today," Buckley said.

"We were (unsure) whether he was going to get to round 23 or not, and he has still got two or three main sessions to go to prove his fitness for that.

"We want to win every game we play and I think that we need to give ourselves the best chance of finishing top four. If we had players available (in round 23), we'd play them."

Buckley added that Jordan Roughead was likely to again play in the forward line after providing the Pies with a solid tall target last week.

Australian Associated Press