But Rodrigo Bentancur brushed aside concerns about the twice world champions' form and said they would be in top shape for their second game of Group A.
"The first game is over and nerves are easing a bit," the Juventus midfielder told reporters.
"The other day the game was a little slow. We all lacked a little mobility," said Bentancur, vowing the South Americans would be faster and get the ball forwards.
A victory against low-ranked Saudi Arabia and Russia in their final group games will be good preparation for what will undoubtedly be much stiffer test in the last 16, where they will probably face either Spain or Portugal.
Uruguay are determined not to be complacent, given that tournament favourites Brazil, Germany, Spain and Argentina all failed to win their first games.
"It's a very even World Cup," said winger Cristian Rodriguez.
(Writing by Alexandra Ulmer, editing by Pritha Sarkar)
