After two loans, at Gil Vicente F.C. and U.D. Leiria (where he first made an impact in the Primeira Liga championship), Douala moved to Sporting Clube de Portugal, scoring five league goals in his debut season while also helping the "Lions" to the campaign's UEFA Cup final, notably scoring against Middlesbrough in a 3–2 away win. Never an undisputed starter, however, he would be loaned for 2006–07 to England's Portsmouth on the very last day of the summer transfer window, with a view to a permanent signing.