Real Madrid’s Cristiano Ronaldo left Portugal’s training session early on Thursday withe an ice pack of his knee and complaints of leg cramps.

Participating in team drills for about 15-20 minutes, Ronaldo left during the ball drills and did not continue practice with the rest of his team, signing shirts on the sidelines and icing his knee instead. Ronaldo has been suffering from tendonitis problems before arriving in Brazil and did not participate in of Portugal’s pre-World Cup friendlies against Greece and Mexico but started against the Republic of Ireland.

Ronaldo’s injury today adds speculation that he will not be 100% fit for Portugal’s opening match against Germany on Monday in Salvador. Placed in Group G alongside the United States and Ghana, Portugal would suffer a huge setback without their star goal-scorer.

Problems with Ronaldo’s leg surfaced a few weeks ago and led to the Portuguese forward sitting out matches with his club Real Madrid as well as Portugal, but he played for Real Madrid in their Champions League final win against Atletico Madrid.

Ronaldo is listed as the most expensive player in the world, with a contract valued at over £80 million, including a £1 billion buy-out clause, which he received when he transferred to Real Madrid from Manchester United in 2009. He won the Ballon d’Or, FIFA’s award for best player in the world, twice in 2008 and most recently in 2013. He is also the first player to score against every single team in La Liga, and is Portugal’s all time leading goal scorer.

Having first played for Portugal in the under-15 team, he first represented Portugal’s senior team in the 2006 World Cup, scoring his first goal on a corner against Iran, helping Portugal to win 2-0. Ronaldo has scored 49 goals in 110 caps since joining the team in 2011 being named captain in 2008.