The duo both went off injuried in the Rhinos’ defeat to Hull on Friday but McNamara has backed both to bounce back and prove themselves worthy of a place in his World Cup squad.
McGuire, 30, suffered a broken leg after Hull’s Liam Watts fell on him while Watkins, 22, damaged his ankle ligaments.
McNamara said: “They were two really unfortunate injuries and the timing is, obviously, pretty poor for us.
“But that is especially true for the Leeds club who have plenty of injuries themselves and it is a cruel blow for the players.
“Kallum was involved in the autumn games for us last season when he played well and, though Danny wasn’t, they are both part of our 30-man ETS squad.
“Hopefully they’ll both get back for the end of the season and they’ll then be available for selection for the World Cup.