MADRID, Dec. 16 (Xinhua) -- Copa del Rey holder FC Barcelona was forced to work hard before ensuring a place in the fourth round on Tuesday night with a 2-0 win away to third-tier outfit CD Guadalajara.

Although coach Hansi Flick fielded a strong side, with Marcus Rashford and Lamine Yamal starting, Barcelona failed to break down a well-drilled and hard-working Guadalajara defense until Andreas Christensen's deflected header from Frenkie de Jong's cross broke the deadlock in the 77th minute.

Rashford, who had earlier had two efforts well saved by Guadalajara goalkeeper Dani Vicente, scored Barcelona's second in the last minute from Yamal's pinpoint pass.

Lucas Beltran and Dani Raba scored goals early in each half to see Valencia to a comfortable 2-0 win away to second-tier Sporting Gijon.

A first-half strike from Adam Boayer saw Elche clinch a narrow 1-0 win away to a heavily rotated Eibar side, while Real Sociedad also progressed to the last 16 with a 2-1 win at third-tier Eldense thanks to Pablo Marin's injury-time winner.

Luka Sucic had put Real Sociedad ahead in the 79th minute before Nacho Quintana equalized just two minutes later, with the game looking set for extra time until Marin's late intervention.

Deportivo La Coruna caused the only minor surprise of the day, with the second division promotion chasers winning 1-0 at home to Mallorca thanks to Noe Carillo's strike five minutes from time. ■