Sydney Roosters young gun Sam Walker has been dealt another setback in his return from injury, reportedly breaking his thumb on Thursday.

The halfback hasn't played in the top grade since Round 26 last year.

In that game - against the Canberra Raiders - he and now South Sydney hooker Brandon Smith both suffered ACL injuries, putting a significant dent in the tri-colours' run to the finals.

Walker returned through the NSW Cup last weekend and by all accounts was strong across a half of rugby league, with coach Trent Robinson recalling him to the top grade on the back of the performance.

But News Corp are now reporting Walker is booked in for surgery on Friday and will spend another four weeks on the sideline as he recovers from the latest setback.

It's understood Robinson will reverse the changes he made on Tuesday, with Hugo Savala going back into the halfback jumper, while Sandon Smith, who has been linked with a departure from the club at the end of the year, had been dropped to the bench.

Smith's reported departure links came about after the Roosters reportedly signed Daly Cherry-Evans for next year, although that deal is still yet to be made official.

Smith and Savala have been performing well above expectations to have the decimated Roosters, who lost a host of other talent to rugby union and the English Super League at the end of last year, in the mix for a spot in the finals.

Walker's new return timeline will see him miss Round 15 and 16 against the Newcastle Knights and North Queensland Cowboys, as well as Round 18 after a bye against the Wests Tigers, before being a chance to return at Kogarah on July 12 in Round 19 against the St George Illawarra Dragons.