GEELONG midfielder Mathew Stokes will miss the vital clash against North Melbourne at Simonds Stadium on Sunday due to an Achilles strain.

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The 30-year-old was injured early in last Saturday's game against Gold Coast.

After battling through until half-time, he was subbed out of the game and has been diagnosed with a minor Achilles tendon strain.

Geelong physio Mark Young told the Geelong website that Stokes would miss at least a week.

"He's feeling better. Scans have shown no significant damage," Young said.

"However he is unlikely to play this week."

The condition of veteran defender Tom Lonergan will be monitored this week after he copped a knee to the head during a marking contest against the Suns and suffered concussion.

"He got a significant blow to the back of the head. He is being monitored closely by our doctor and any decision on him will be made later in the week," Young said.

Geelong will also be without Jimmy Bartel who is due to have surgery on Thursday to repair his strained medial ligament.

He is expected to be out for six weeks while Andrew Mackie remains sidelined with a quad strain.