Diego Costa
Costa was not very impressive in the 2014 World CupReuters

Chelsea striker Diego Costa has expressed his disappointment after his injuries have once again prevented him from playing for Spain.

The 26-year-old, who also unable to link up with his national side in November due to an injury, was again ruled out of Spain's upcoming international fixtures against Ukraine (2016 Euro qualifying) and Netherlands (friendly) after suffering a level one hamstring tear during Chelsea's 3-2 win over Hull on Sunday.

And the Brazil-born striker says that he is bitterly disappointed.

"I was in good form, I thought everything was finally going to work out," Costa told Spanish sports newspaper Marca.

"You always arrive [to the national team] with some aches. But this time, I would have arrived without any pain. I really wanted to prove my form and my worth... but again it [injury] happened."

The former Atletico Madrid player insists that his "history" with the national team has not started and he is itching to prove his worth.

"My history with the national team is that it still hasn't really started," the 26-year-old said. "I haven't done anything yet. The national team is something I think of."

"I am sorry that I cannot bring what I would like to. Something always happens when I get close to playing for Spain. It bothers me from a personal standpoint but I hope this will end. I've gone through a lot to be in the national team and I hope good times will come."

Costa, who was very disappointing for Spain in the 2014 World Cup last summer, says that he is looking for success with the national team.

"I am looking to succeed with Spain," he added "The national coach and my teammates are counting on me. They deserve to be paid back for the confidence that they placed in me. I hope I can do that on and off the pitch."

Costa's constant absence from the international scene due to injuries had resulted in some people questioning his commitment to the national team.

But the striker insists that he can only silence his critics once he starts performing for Spain.

"Sometimes it angers me that they put in doubt my commitment," he said. "I already proved that I'm enthusiastic and that I want to achieve success with the national team.

"The best way to silence the critics is to play and to do things well. But I haven't done that yet and hence, I have to listen and swallow [criticism].

"It is one thing is to criticise my performance, which is fair, but another to criticise my commitment."