New signing Patrick van Aanholt made his Sunderland debut as the Black Cats lost 1-0 in their pre-season friendly with CD Nacional in the Algarve.
Forward Lucas scored with an 89th-minute volley for the Portuguese side.
Defender Billy Jones almost got his first goal for Sunderland, but his shot from six yards was saved by Nacional goalkeeper Eduardo Gottardi.
Netherlands international Van Aanholt, signed from Chelsea for an undisclosed fee, hit a long-range strike just wide.
Striker Connor Wickham also had three efforts saved, while defender Wes Brown headed a chance over the bar.
Sunderland (4-1-4-1): Pantilimon, Jones (Mavrias 46), Van Aanholt (Roberge 81), Brown, O'Shea, Cattermole (Bridcutt 60), Gomez, Johnson (N'Diaye 75), Giaccherini (Ba 80), Wickham, Fletcher.