The Newcastle United pair are progressing well with their respective injuries.
Spanish midfielder Merino has missed Newcastle's last three games with a back injury, while left-back Dummett has been sidelined since the first day of the season with a hamstring problem.
The Magpies host Watford on Saturday and although Benitez did not reveal whether the pair will be involved, he did disclose that they are making positive strides in their return to the squad.
"Merino’s been doing part of the training session, and Dummett has done the full training session, so that’s positive news for us," he told The Shields Gazette.
Benitez's side have coped in the absence of Dummett, with Javier Manquillo, Chancel Mbemba and Jesus Gamez filling in that left-back role to good effect.
But the same can't be said for Merino, who has been sorely missed.
United have lost all three games that the former Borussia Dortmund man has missed, since scoring the 86th-minute winner against Crystal Palace on October 21.
He has been arguably Newcastle's best player this season and the sooner they get him back, the better.