Barca's place in a fifth final in six years was assured after a 7-0 first-leg rout last week and without their star attacking trio Lionel Messi, Luis Suarez and Neymar the under-fire Neville looked set to be handed some relief by Alvaro Negredo's first-half opener.

However, 19-year-old Cameroonian midfielder Wilfred Kaptoum came off the bench to score his first Barca goal and preserve the European champions unbeaten run six minutes from time.

Sevilla are well-set to meet Barca in the final on May 21 as they travel to Celta Vigo in the second-leg of the other semi-final on Thursday leading 4-0.

In total, Barca boss Luis Enrique left 11 first-team regulars back in the Catalan capital with an eye to his side's busy upcoming schedule in La Liga and the Champions League.

By contrast, Valencia find themselves in the midst of a relegation battle in La Liga having not won for 12 league games, including nine since Neville took charge in December.

And Neville also left out some of the most important members of his squad for the crucial clash at home to Espanyol on Saturday which looks set to decide his future at the club.

However, there was some relief for the England coach as Negredo, who has cost his side with a series of vital missed chances in recent weeks, finally found the net.

The former Manchester City striker was afforded a huge amount of room in behind the Barca defence to open the scoring six minutes before the break and, despite firing his first effort straight at Marc-Andre ter Stegen, the rebound fell favourably for him to tap home his ninth goal of the season.

Both sides went through the motions in the second-half in front of a crowd of barely 15,000 at the 55,000 capacity Mestalla.

However, Neville was denied his biggest win since arriving at the Mestalla late on when Juan Camara's cross picked out the unmarked Kaptoum to slot home from close range.