ESSENDON forward Matt Guelfi will miss the the early stages of the season after suffering a hamstring strain at training last week.

The 27-year-old injured the hamstring prior to Christmas but had been progressing well, having spent part of the off-season visiting soft-tissue specialists in the USA.

But in a fresh setback, Guelfi re-injured the same hamstring and will now undergo surgery early next week.

He is expected to be sidelined for 10-12 weeks. 

"'Guelf' was progressing well in the rehab of the injury he sustained pre-Christmas, so it's really disappointing to see him suffer another setback," Bombers footy manager Daniel McPherson said.

"He'd spent part of his off-season visiting soft-tissue specialists in the USA, and together with our medical team was implementing what he'd learned overseas into his pre-season program.

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"It's frustrating that he hasn't been able to get a clean run at it to this point.

"While surgery will keep him sidelined for the next few months, we're confident we'll get to see 'Guelf' back out there playing plenty of strong footy for us this season."

It's the second hamstring setback for Essendon within the week, with defender Jordan Ridley also suffering a minor hamstring strain, ruling him out of the Bombers' match simulation against the Western Bulldogs.

As reported by AFL.com.au, Alwyn Davey jnr underwent minor knee surgery recently which is expected to sideline him for up to six weeks.

In better news for the Bombers, Ben McKay (ankle) is set to return to full training in the coming weeks, while Nik Cox (concussion) is increasing his training loads.

Essendon kicks off its pre-season with a scratch match against the Western Bulldogs at Mission Whitten Oval on Saturday, February 15, before facing Geelong at GMHBA Stadium on Thursday, February 25 as part of the AAMI Community Series.