The visitors emain one of a number of clubs still in the mix to qualify for Europe for what would be just the second time in their history, and they nearly made a dream start here. Inside two minutes, Betis goalkeeper Claudio Bravo denied Alvaro Garcia with a sublime one-handed save before Isi Palazon hit the rebound against the foot of the post.
After coming within inches of breaking the deadlock only three minutes prior, Rayo were left rueing their missed opportunities, as Betis spectacularly took the lead from the unlikeliest of sources.
Youssouf Sabaly netted his first LaLiga goal in sensational fashion, as the Senegalese full-back unleashed a ferocious effort from outside of the area that flew into the top corner.
The visitors continued to come forward, and once more Bravo stepped up to preserve his side’s lead, tipping another Palazón effort against the woodwork. It was an intervention that would prove vital as on the stroke of half-time, Betis netted again.
Ayoze Perez instinctively got the other side of Ivan Balliu, which allowed the Leicester City loanee to poke Willian Jose’s headed flick-on past Stole Dimitrievski.
Referee Juan Pulido became public enemy number one after the restart, as he waved away the hosts’ appeals for a penalty after it appeared that Fran Garcia had handled the ball in the area.
The man in the middle drew the ire of the Betis players again moments later, as his refusal to blow up for a rash-looking challenge on half-time substitute Andres Guardado allowed Santi Comesana to plant a flying diving header past Bravo to reduce the arrears.
Hell-bent on completing a sensational second-half comeback, Rayo then unbelievably struck the woodwork for the third time in the match, with Oscar Trejo’s dipping effort hitting the top of the bar - which ultimately turned out to be the visitors’ last significant chance of salvaging a share of the points.
After withstanding a period of pressure, Betis frontman Borja Iglesias put the result to bed with a 97th-minute strike to secure just a third victory in eight league matches that ensures Manuel Pellegrini’s men keep their destiny in their own hands, now boasting a seven-point gap to the chasing pack in the race for the European places.
Meanwhile, Rayo missed the opportunity to move above four sides into the sole Europa Conference League qualification position after failing to win for a 10th time in the last 11 meetings.