England had a fairly mediocre group campaign, topping Group B with wins over Paraguay and Trinidad & Tobago and a draw with Sweden but without really showing much flair.
They will count on striker Wayne Rooney rediscovering his best form, which he only hinted at in the two games he played on returning to the team after breaking a bone in his foot.
With fellow forward Michael Owen ruled out through injury, coach Sven-Goran Eriksson is likely to use Rooney as a lone striker supported from midfield for the game in Stuttgart.
Ecuador will look to repeat convincing wins over Costa Rica and Poland in Group A, and attempt to banish memories of their 3-0 drubbing by Germany in the tournament's opening game.
The second round match could also be a test for the England fans' behaviour. With a history of soccer-related violence, they have been closely watched throughout the finals.
For the most part there has been little trouble but on Saturday they clashed with German fans in Stuttgart, throwing bottles and chairs before riot police restored order.
About 100 England fans were detained.
Police have warned that as the tournament progresses tension could rise since defeats now mean instant elimination.
In Sunday's other last 16 game Netherlands face Portugal in Nuremberg hoping to avenge a 2-1 semi-final defeat at Euro 2004.
But it will not be easy against a Portuguese side who won all three first round games, albeit in a fairly easy group.
That said, the Dutch have not really been tested so far either since their only tough opponents have been Argentina who by the time they met had also already qualified.
The winners of Sunday's two games will face each other on July 1 in the quarter-finals in Gelsenkirchen.
Already through to the last eight are hosts Germany, who beat Sweden 2-0 on Saturday, and Argentina after their 2-1 extra-time win over Mexico. Those teams meet on June 30.
England play Ecuador at 1500 GMT, while Portugal face Netherlands at 1900 GMT.
