COLLINGWOOD defender Ben Sinclair has signed a two-year contract extension, emphasising his importance to the Magpies' developing backline ahead of his 50th AFL game against Geelong on Friday night.

AFL.com.au understands the terms of the new deal, which will tie the speedy defender to the Magpies until the end of 2017, have been agreed upon for a number of weeks.

Sinclair's 2015 campaign has been hampered by a hamstring injury but the 23-year-old has fought his way back into Nathan Buckley's team and will have played the last four games in the seniors after the match against the Cats.

It follows a frustrating 2014 season, with hamstring troubles keeping Sinclair – who made his debut in 2011 – to just five matches.

Injuries have been an issue for the lock-down small defender, who managed 15 games in 2013 before a shoulder reconstruction ended his year at round 21.

Sinclair, pick No.62 in the 2009 NAB AFL Draft, is highly regarded by the Magpies given his speed coming out of defence and his discipline in sticking to his defensive assignment.

Meanwhile, discussions between the Magpies and young defender Matt Scharenberg continue to progress.

The 19-year-old, who returns to the team for Friday night's game against the Cats, has been heavily linked to a return home to play with either Adelaide or Port Adelaide next season.

However it is believed Scharenberg, the Magpies' first-round pick (No.6 overall) in the 2013 draft, is leaning towards staying at Collingwood and repaying the faith the club has shown in him after foot surgery in 2013 and a knee reconstruction in 2014.

Scharenberg is set to play his third AFL game against the Cats after making his debut against Melbourne in round 18.