SCANS have revealed North Melbourne's Nathan Grima has suffered a high grade medial ligament strain and will be sidelined for four-to-six weeks.

Grima copped a heavy knock to his knee in the first quarter of the Kangaroos' round one NAB Cup game against Richmond at Etihad Stadium on Friday night.

Kangaroos coach Brad Scott said although the club's initial assessment of Grima's knee suggested his anterior cruciate ligament had not ruptured it still feared Grima was facing time on the sidelines.

"To be honest it didn’t look great to me," Scott said after his teams' loss to Hawthorn in its second game on Friday night.

"The physios (and) doctors at first glance … think his ACL is well and truly intact, but you don’t really know definitely until you go and get it assessed."

Scott was proven correct with Grima now in doubt for the Kangaroos' season opener against Essendon.

Minutes before Grima limped off, teammate Leigh Adams was involved in a heavy collision with Tiger Reece Conca and lay prostate on the ground for some time before walking from the ground.

Scott said Adams was "dazed and confused", but had been cleared to go back on the ground. However, he said North had not wanted to take any risks with him.

On a more positive note, Scott sung the praises of third-year midfielder Ben Cunnington. After being selected by the Kangaroos with the No. 5 pick in the 2009 NAB AFL Draft, Scott said his on-ball performances against the Tigers and the Hawks suggested he was ready to repay North's faith.

"Three years on, he's starting to look like a genuine AFL midfielder, so that's pleasing," Scott said.  

Scott was also happy with Robbie Tarrant's first outing as a forward at senior level.

"He's starting to look like the key-position player we drafted (at No. 15 in 2007)," he said.