St Kilda forward Stephen Milne has begun a cross-country road trip as he recovers from a fractured cheekbone suffered in Sunday's AFL win over Fremantle.

When his teammates on Tuesday begin their preparation for Sunday's vital game against Adelaide, Milne will be driving across the Nullarbor Plain after being ordered not to fly home from Perth.

Milne spent Sunday night in Perth after the Saints' win at Subiaco Oval, after he was diagnosed with a small crack in his right cheekbone, which he suffered in a collision with Docker Antoni Grover.

Milne and a St Kilda official began driving home and are expected to arrive at the club on Wednesday.

"With that sort of injury he was told not to fly, so he'll be assessed by our doctors when he gets back," a club spokesman said.

Milne bravely played on after the first-quarter clash, but is unlikely to play in round 21, where the eighth-placed Saints take on the fifth-placed Crows.

Collingwood expect young gun Dale Thomas to play Sydney on Saturday night despite him straining the back of his knee in the win over Port Adelaide last Friday night.

Meanwhile, the AFL will this weekend field four boundary umpires per game as part of a plan to have the extra officials in place come the finals, to prevent against potential mistakes.

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