​Spain boss Julen Lopetegui has advised Diego Costa to try his best to sort things out on the transfer front if he wants to regain his place in the national team.

The combustible striker has exiled himself from Chelsea ever since that infamous text from Antonio Conte and is training on his own in a bid to maintain fitness levels.

Arsenal v Chelsea - The Emirates FA Cup Final

After failing to force a move to Atletico during the transfer window, the Spain international has been left in the wilderness, and has no hope of playing regular football in 2017.

The Blues named Costa in their Premier League squad for the season, but he never did show up.

Lopetegui, meanwhile, has urged the Brazil-born forward to sort himself out as he won't be able to get back into his squad without training and playing.

"Costa’s summer has been unusual, strange, complicated – not just for him but for his club," the coach said to beIN Sports (H/T ​Metro). "He is still a Chelsea player. It’s a complicated issue.

"Our hope is that he will resolve his situation as soon as possible and that he can compete, train and play, which is what he likes doing the most and what interests the national team.

Arsenal v Chelsea - The Emirates FA Cup Final

"It’s rather complicated that a guy who doesn’t train and doesn’t play can be with us, but that’s all it is.

"He wasn’t ready to play with us (against Italy and Liechtenstein), that was the reality and what we had to deal with. That is the reason why he wasn’t with us.

"He needs to train and play in order to be considered."

Since Lopetegui's statement, both Chelsea and Atleti have confirmed that a deal is in place to see Costa return to Spain, subject to personal terms and routine physical checks.