Johnson is in doubt for Saturday's match against Parramatta in Auckland after suffering a painful blow to his left forearm during their 18-6 win over Canberra on Sunday.
The playmaker, who played on after undergoing treatment in the first half after he was jammed in a tackle, is likely to need a scan this week.
Tomkins, who set up two tries, struggled through the latter stages of the Raiders game with a leg complaint, but coach Andrew McFadden says the English speedster has no ongoing issues.
Centre Konrad Hurrell's knee injury could keep him out for another week, having suffered damage in the opening round loss to Newcastle.
Three forwards are likely to be available after shaking off niggles - hooker Siliva Havili, back-rower Raymond Faitala-Mariner and prop Charlie Gubb.
Prop Sam Rapira and outside back Ken Maumalo are likely to remain sidelined this week because of hamstring complaints while there is no definite time frame for centre Ngani Laumape (knee) to return.
