The first leg in Seville three weeks ago saw Quique Setien's side take a two-goal lead, only to concede late on and give Los Che a healthy away goal advantage.
Valencia boast an excellent home record this term and are unbeaten in their last 13 matches in front of their own fans, so will certainly fancy themselves to reach the final.
William Hill price a victory for Marcelino's side at 8/11 (1.73) with Valencia offered at 1/3 (1.33) to qualify. Betis, for their part, are priced at 18/5 (4.60) to win in 90 minutes and at 9/4 (3.25) to make it through to the final.
Centre-back Ezequiel Garay will miss the clash for Valencia, while substitute goalkeeper Jaume Domenech will keep his place between the sticks.
Betis are likely to be without attacking wing-back Junior Firpo.
There is a lot on the line for both sides on Thursday evening, with a Copa del Rey final appearance likely to be one of the defining aspects of their respective seasons.
Betis know they must score to progress but Valencia do have a strong scoring record at home, and while neither side have maybe been as prolific as we would have expected this term, there should be goals once more on Thursday evening.
Los Che have netted in 15 of their 20 home matches in all competitions this term while Betis have scored in nine of their last 12 competitive games on the road.