Spain captain Rodri warned Portugal on the eve of Monday's World Cup last-16 clash that the European champions can still get a lot better.

Spain, one of the favourites in North America, were held to a shock 0-0 draw with debutants Cape Verde to open their title charge.

They then beat Saudi Arabia 4-0 and Uruguay 1-0 to top their group, before a statement 3-0 win over a dogged but limited Austria in the last 32.

That impressive performance served notice to their rivals, and midfield general Rodri said that was just the start.

"Spain's evolution (at the tournament) has been gradual," the 30-year-old Manchester City ace told reporters on Sunday ahead of the meeting with Cristiano Ronaldo's Portugal in Texas.

"Obviously in a sense that is normal - in the first games you try to adapt to a different environment, different pitch, different type of teams you face, it is never easy.

"So I think in a gradual way, always growing and always knowing that the big things are coming now."

Spain's goalless stalemate with Cape Verde came as a huge surprise, but Rodri said: "We didn't lose our heads, we stayed calm, and I think right now we still have a big gap of improvement."

AFP