It seemed as if Spain were heading for another poor result until Mendez fired in after keeper Ibrahim Sehic failed to hold onto to Isco's shot.

Chelsea's Alvaro Morata should have given Spain the lead but he missed an awkward chance from four yards out.

Real Madrid forward Marco Asensio also also spurned two good chances.

The result might come as some sort of consolation for Spain coach Luis Enrique after his side's participation in the inaugural Uefa Nations League was ended by England's victory over Croatia, three days after they were beaten 3-2 by the Croats.

Spain barely troubled the visiting defence up until the goal.

Long-range efforts from Suso, Isco and Asensio lacked accuracy, while Bosnia's defence coped comfortably with Spain's attempts to cut through them.

Asensio, with only three goals for club and country this season, should have nodded La Roja into the lead, but sent his header wide by two feet.

He then managed to test Sehic with a shot that was parried into the path of Morata. However, the ball came at the Blues striker at such speed he could not adjust his feet to tap home into the empty net.

Mendez came on soon after, and scored the match-winner 13 minutes from time when he tucked in after Isco's low drive was parried.

He became the first player to score on his debut for Spain since Iago Aspas in November 2016 against England.