Del Bosque recently admitted his disappointment with the striker's performance at a national level.
Mata says team-mate De Gea will know how to put his failed transfer to Real Madrid behind him.
Mata expresses delight at returning to Spain squad for the first time since the World Cup.
Costa has scored just once in seven appearances for the national team.
The cave in Barcelona was once a cosy home to a caveman.
Number of deaths as a result of goring by bulls in Spain in 2015 rises to 12
Workers in Cristovo de Cea mistook slabs of ancient tomb for broken bench.
170 tonnes of over-ripe tomatoes were flung in the yearly festival.
The 20-year-old Spanish man asks father for ransom through fake kidnapper.
Female animal rights activist bravely comes to the rescue of a dying bull before being pulled out of the ring.
The 18-year-old died of his wounds in the northern town of Lerin
BREAKING: Local media reports that boy fell into pool while parents hosted dinner party.
Spain's Extremadura local authority fined over death blamed on "poor route signage".
A woman said to be suffering from psychiatric issues was arrested after a baby's body was found.
Young man is gored to death after standing in the path of a bull run while filming using his mobile phone.
Health warnings in place as heatwave spreads across Europe.
King Felipe seen sailing while Queen Letizia spotted for the first time since her grandfather died.
Man attempted to smuggle himself into country in suitcase in boot of car.
Kleyo De Abreu, 23, from London, died after she hit her head on the Tablate Bridge during a jump.
Malaga OAP claimed that the man had 'fallen from the sofa'
Pair allegedly lured women to Spain with promise of jobs, and forced them into prostitution using voodoo.
The French citizen suffered serious injuries during the Pamplona festival in which bulls run through the village streets.