HULL KR back-rower Rhyse Martin suffered a broken foot in the club’s win over Huddersfield Giants last Saturday.
Rovers secured a 52-12 victory over Huddersfield at the Accu Stadium in the Challenge Cup fourth round to set up a home tie with York Knights in the quarter-finals.
PNG international Martin converted eight of their nine tries but will be out for the next month with his injury.
It means he will likely miss that York match on the weekend of April 10-12, plus the Good Friday derby with Hull FC – also at Sewell Group Craven Park – which precedes it.
Hull KR, who have won only one of the first three games of their Super League title defence, next travel to Catalans Dragons this Saturday and host St Helens on Friday, March 27.
While injuries have been the talk of the competition in the early rounds, the only other first-choice Hull KR player currently sidelined is fullback Arthur Mourgue, who suffered a pectoral injury in their World Club Challenge victory last month.
However, that does mean the Robins are now without their top two goal-kickers for the coming weeks, a role likely to be given to Mikey Lewis.