Barcelona left-back Jordi Alba said Isco is one of the best players in the world, but he does not enjoy watching his Real Madrid rival playing at such a high level.
Isco has flourished under Zinedine Zidane, cementing himself in the starting XI at Spanish and European champions Madrid with four goals and three assists in LaLiga.
The 25-year-old has outdone four-time Ballon d'Or winner Cristiano Ronaldo this season and Alba painfully heaped praise on his Spain team-mate prior to Saturday's international friendly against Costa Rica.
"Comparing is never good. I've known him for many years," Alba told reporters.
"He is at the same level as the best in the world and I don't like to see our greatest rival in that kind of form.
"Everything that you can say about him is good. We crossed paths at Valencia and I know him very well."