Rayo enter the match off the back of a four-match unbeaten run in the league, with Jemez's side currently two places and a point above Osasuna, who sit 17th.
"We've got to try and keep up our good run and although the game isn't definitive or a final, it would give us breathing room," Jemez told reporters at a press conference.
"We just have to win, play well and take the points. It's possibly the most important game we'll play this year. Hopefully I'm right about that."
Real Betis, Real Valladolid and Getafe currently sit in the drop zone.