Elche, meanwhile, managed a 2-1 win over Valencia in their previous league fixture - putting them two places above Betis in the table, despite playing two fewer games.
Betis have now failed to score since October 3 - registering another disappointing loss against Real Sociedad two weeks ago, losing 3-0 against the Basque outfit.
Los Verdiblancos have struggled with consistency this season, with new boss Pellegrini failing to pick up a win since before the international break.
Newly-promoted Elche, on the other hand, are currently on a four-game unbeaten run, having gained an impressive three wins and one draw in their last four matches.
Valencia were able to claw one back in the 74th minute with a goal by Toni Lato - resulting in a rather nervy ending for the hosts, as Gonzalo Verdu cleared a chance off the line in the dying moments of the game.
Los Franjiverdes have also kept three clean sheets in the league - an impressive stat heading into Sunday's game.
The two teams last met back in 2014 in a friendly, where Elche came out victorious in a 2-1 scoreline.
Just a few months prior, they faced off in La Liga - with the score ending in a dull 0-0 between the two teams.
Real Betis La Liga form: LLWLLW
Elche La Liga form: WWDWL
Elche form (all competitions): WWDWLL
Following his red card against Atletico, Montoya is suspended for the upcoming home game - leaving Pellegrini with few options at right-back. Emerson is likely to replace him in defence if the Brazilian is deemed fit enough.
Elche only have one injury doubt going into this game, with striker Guido Carrillo currently tackling a knee problem.
Real Betis possible starting lineup:
Bravo; Emerson, Mandi, Bartra, Moreno; Rodriguez, Carvalho; Fekir, Canales, Tello; Sanabria
Elche possible starting lineup:
Badia; Barragan, Verdu, Josema; Josan, Marcone, Guti, Fidel; Morente, Milla, Rigoni
We say: Real Betis 1-1 Elche
Elche are currently in superb form, however Betis will be desperate to get back to winning ways - and will see this game as a great opportunity to secure at least a point. Therefore, we reckon a 1-1 scoreline will be the likely result of this match.