Another knee injury to luckless Richmond defender David Astbury was one of the more heart-wrenching moments of yesterday’s loss to Melbourne, according to coach Damien Hardwick.

Astbury was having his best season since being drafted in 2009, before he went down with a dislocated kneecap in the second half.

"You only have to see what it means to the kid - to see tears in his eyes at three-quarter time," Hardwick said.

"He knows what he's done and unfortunately he's going to be a big loss for us.

"We're not exactly sure of the extent."

The injury happened in red time in the third quarter when Astbury went to change direction when he tried to tackle Jack Viney in the Demons' attacking arc.

His left leg twisted and collapsed beneath him as Viney went on to kick a goal.

He appears to have suffered the same injury he sustained to his right knee in round 12, 2011 – a patella dislocation with medial ligament damage.

He needed two operations after that injury and missed nearly 12 months, not playing seniors again until round 22, 2012. 

The brave backman joined his teammates at three-quarter time on the field, aided by crutches and with a bag on ice on his knee.

Just two weeks after regaining key defender and Astbury's good friend Alex Rance, the Tigers will again have to reshuffle their back six to cover the loss.

A shattered Hardwick acknowledged how influential Astbury had been this season after finally being able to put together a full pre-season.

"It's a real shame, he's been a very good player for us," he said.

"He's been one of the shining lights this year. He's kept a lot of good players goalless.

"To lose him in a similar manner to what he's done previously is really disappointing."