Gertjan Verbeek\'s side caused an upset in last week\'s first leg but Willie Duncan expects Unai Emery\'s team to turn things around and qualify for the Europa League semi-finals.Progress to the latter stages of European competition has become something of a norm for Spanish sides in recent years and Valencia are strong favourites to keep that trend going by qualifying for the semi-final stage of this year’s Europa League when they host Dutch outfit AZ in the second leg of the last eight.Maarten Martens’ goal 10 minutes from time in the first leg has given the Dutch side a slender advantage going into Thursday’s return clash at Mestalla. Despite a 2-1 deficit, the Spanish club are hot favourites with bookmakers 188Bet chalking them up at just 9/20 (1.45) to win Thursday’s game.AZ have largely been written off by the bookmakers and 188Bet makes Gertjan Verbeek’s men a chunky 11/2 (6.50) to follow up on victory from the home leg with a shock win in Spain while the same firm go 29/10 (3.90) that the match finishes all square after 90 minutes.Despite their status as overwhelming favourites, Valencia have been in stuttering form of late, recording just a solitary win in their last seven matches.Such a dip in form at this time of the season will be a concern for coach Unai Emery ahead of this important match but Valencia can be trusted to bounce back here and record a victory given the depth of quality in their squad.A 2-0 victory for the home side would be enough to see them into the semi-finals and such an outcome is rated as a 7/1 (8.0) shot with 188Bet while a 3-1 victory is a 10/1 (11.0) chance with the same firm.However, given how out of sorts Valencia have been, a nervous performance could be expected and should the Spaniards fail to find their free-flowing form, the 16/5 (4.20) quote from 188Bet for the tie to be level at half-time with Valencia eventually prevailing in the second half carries considerable appeal here.