MATT de Boer's chances of an early-season debut with Greater Western Sydney have been dashed by a hamstring injury.

De Boer, 26, tore his hamstring at training on Monday and will be on the sidelines for the next 4-6 weeks.

The former Fremantle midfielder has been training well since arriving at GWS in November, and along with a host of other senior players, was rested from last week's opening round of the JLT Community Series against West Coast in Narrandera.

He looked set to play his first game for the club against the Swans on March 3rd, but the injury means it's unlikely de Boer will play any footy before round two or three of the regular season, making his job of cracking a spot in Leon Cameron's best 22 even tougher.

GWS Head of Athletic Performance David Joyce said the injury was cruel timing for the Giants' recruit.

"Matt (de Boer) has contributed really well to our playing group throughout the pre-season," he said.

"This is obviously a disappointing setback for Matt but no doubt he'll do his rehab very diligently to return to the field in the coming weeks."

Despite solid form in the WAFL last season, de Boer struggled for opportunities at the Dockers in 2016 and played just four senior games for the year, but was seen as a valuable addition to the depth of the Giants' list, given his 138 games of experience, versatility, and professionalism.

The tough onballer won Peel Thunder's WAFL best and fairest last year and finished runner-up in the Sandover Medal despite only playing 12 regular season games, then helped the club to its inaugural premiership with 30 possessions and 14 tackles in the Grand Final win over Subiaco.