The two players hopes of playing in the Spanish top-flight took a major blow as their clubs suffered heavy defeats in the playoff ties
Umar Sadiq endured a frustrating night, while Kenneth Omeruo was an unused substitute as both Leganes and Almeria now need a miracle to progress to the La Liga Smartbank promotion playoff final.
Both Almeria and Leganes missed out on automatic promotion and were paired against Girona and Rayo Vallecano, respectively, in the playoffs semifinal.
Sadiq, who scored 20 goals in 38 league games for Almeria during the regular season, fired blanks as La Unión suffered a 3-0 defeat away from home.
The former Rangers star was on the pitch for the entire duration, but he could not prevent Almeria from a damaging loss.
Almeria got off to the worst possible start as Édgar Bárcenas and Yan Couto put Girona two ahead inside the opening five minutes.
It stayed like that until Mamadou Sylla added a third in the 68th minute, leaving Almeria with a mountain to climb going into the second leg.
Meanwhile, Omeruo also suffered a similar fate as Leganes suffered a 3-0 loss at Rayo Vallecano. The 27-year-old, who, along with Sadiq, is not in the Super Eagles squad for the Cameroon clash due to the playoffs, was on the bench for the whole 90 minutes.
Neither side could break the deadlock in the opening half, but Rayo scored three second-half goals courtesy of an Alvaro Garcia strike and a Bebe brace to put themselves in the driving seat.
The second leg of the two games takes place on Friday and Saturday, with Almeria hosting Girona before Leganes welcome Rayo.