Newcastle Knights centre Bradman Best continues to have his State of Origin return under a question mark, with a hamstring issue continuing to plague his preparation.

The centre, who had only just returned from a previous hamstring issue at club level, has managed a single game for the Knights before being selected for Origin 3.

That came after another injury, with South Sydney Rabbitohs' star Latrell Mitchell suffering a foot injury during the South Sydney Rabbitohs' win over the Parramatta Eels last Thursday.

Mitchell himself had only come into the side for Joseph Suaalii, who was suspended following a devastating high tackle that saw him sent off in Game 1.

The Blues' revolving door in the centres may not be settled yet though, with the revelation Best still didn't train with the side on Thursday during an opposed session against the St Marys Saints.

NRL.com report that Best, who trained away from the side on Wednesday, was again warming up away from the side on Thursday morning before media left the facility.

Fox Sports are reporting that the Blues are confident Best will be fit to take to the field in Brisbane next Wednesday, but his limited preparation must surely now becoming a cause for concern in the Blues' camp as they prepare to break a long run of Queensland winning deciders at home.

18th man Matt Burton is understood to have trained in the centres for Michael Maguire's side so far this week, and could well be asked to play the role during the game if Best doesn't pass fit, with the Blues likely to make a call on Saturday once assessing the Knights' centre again.