Cristiano Ronaldo is doubtful for Portugal's friendly with Liechtenstein after picking up the flu in Real Madrid's recently-concluded US tour. "Ronaldo returned from Washington DC with a common type of flu and has been told to rest at home and has been prescribed to medication," Real said in a statement. Ronaldo played as Real thrashed DC United 3-0 on Sunday, courtesy of goals from Gonzalo Higuain (twice) and Arjen Robben. Portugal will visit minnows Liechtenstein on Wednesday, before taking on Denmark in the World Cup qualifiers next month.