That reliability makes Costa an interesting alternative for defending champion Spain, which has watched Fernando Torres' erratic play with Chelsea. The 23-year-old Costa also has a gritty streak.
''Diego has a particular character that makes up a big part of his game,'' Senna said.
Costa played a few minutes for Brazil in exhibitions against Russia and Italy in March but never appeared in a competitive match, leaving him eligible for Spain - which doesn't have another official match until the World Cup in June.
A leg muscle injury prevented him from making his debut for Spain in Saturday's exhibition against Equatorial Guinea. His next chance will come on March 5 when Spain plays an exhibition against Italy.
Costa said making himself available to Spain was his way of repaying the country where he's been successful as a professional.
''It's a complicated decision because it's a decision related to the country where you were born against the country that has given you everything,'' he said. ''I hope people can understand and respect this decision, which was very difficult to take.''
Senna said choosing to play for Spain was ''the easiest decision of my life.''
But Marcos Senna completely understands Costa's decision to play for his adopted country.
Like Costa, Senna also was born in Brazil but played for Spain. He expects the furor over the forward's choice of national team to dissipate.
''I don't see any reason for such polemic,'' Senna, a 2008 European Championship winner with Spain, said in a telephone interview. ''While it is a heated issue right now, I think come the World Cup, people will be focused on their own teams.''
Dozens of naturalized players have turned out for Spain over the years. The most famous are Argentina-born Alfredo di Stefano, who made 31 appearances for Spain, and Hungarians Ferenc Puskas and Laszlo Kubala.
Costa moved to Europe in 2005, signing first with the Portuguese club Penafiel and then spending spells in Spain with Celta Vigo, Valladolid, Rayo Vallecano and now Atletico Madrid.
''From the very first minute, you feel like a privileged person to be pulling on the jersey,'' said Senna, who spent 11 seasons at Villarreal. ''It's reciprocal. You want to thank the people with your on-field play for all the care and attention they show you.''
Brazil coach Luiz Felipe Scolari was among those critical of Costa's choice. He accused him of turning his back ''on the dream of millions.''
Spain coach Vicente del Bosque has been welcoming.
''Nobody chooses where they are born,'' Del Bosque said. ''The national team is not a closed club, everyone will be well received here.''
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