Grundy began the season as the Pies' first choice in the ruck after forcing both premiership ruckman Darren Jolly and Witts from the team in the final seven games of 2013. 

Grundy's form has tapered off this season after a reasonable start, and he has played just one senior game since round 13. 

Buckley said Witts' form has demanded he stays in the side at Grundy's expense. 

"The biggest impact on Brodie's selection has been the form of 'Wittsy' and the fact that he has stood up and really gone to that next level," Buckley said. 

Grundy's form as a 19-year-old after making his debut in round 18 last season flew in the face of the theory that big players often take time to get up to speed at AFL level.

He also looked to have overtaken Witts in the pecking order. 

"Competition for spots is a massive part of players pushing each other to reach new levels, and Jarrod [Witts] was tested with that with Brodie stepping up," Buckley said. 

"He has answered the challenge, and the ball is in Brodie's court to answer it."   

Buckley said the club was impressed with the VFL debut of Matt Scharenberg, the club's first pick from the 2013 NAB AFL Draft, but poured cold water on the idea that the No.6 selection may debut in the seniors this season. 

"There is so much water to go under the bridge before we get to that. Logic would suggest that that is just not going to happen," Buckley said. 

The 18-year-old had both his feet operated on pre-season after battling sesamoiditis, and Buckley said each game between now and the end of the season was a bonus. 

"To expect a young player to come in at AFL level in rounds 21 and 22 off three or four games of VFL and virtually only a month of extra football training beyond that is a bridge too far," Buckley said. 

"I'm sure Matty would be thinking 'if I play really well in the next two or three weeks, I will put myself up for selection', but the likelihood is that we're really keen for him just to get game time, get his legs underneath him and take advantage of playing footy again."

The Magpies are hopeful Luke Ball will be available for selection for Sunday's clash with Port Adelaide after he trained on Wednesday, but Alan Toovey, who did not train, still has several hurdles to jump. 

The Magpies hope defender Ben Sinclair, who has played just two games this season, will be ready to play senior football around round 21.