Melbourne Storm has ruled injured star Harry Grant out from the opening three rounds of the 2021 NRL season.

The club confirmed in a statement on social media that the hooker sustained a high grade MCL strain in Saturday's trial clash against the Knights.

"Scans today have unfortunately confirmed Harry Grant sustained a high grade MCL strain in Saturday's trial," the Storm posted on Twitter.

"It is expected he will be sidelined for the opening three games of the new season."

Grant limped off the field with what coach Craig Bellamy confirmed was a medial ligament injury.

“He’s done a medial so I doubt if he’s going to be ready for Round 1,” Bellamy said post-game.

“I’m not quite sure, it’s probably three or four weeks I’d think, medials usually are.”

It would rule Grant out of the Storm's opening three clashes against the Rabbitohs, Eels and Panthers.

The 23-year old has just returned from being on loan to the Wests Tigers in a breakout 2020 season.

Brandon Smith looks set to assume the No. 9 jersey in his absence.