Christian Pulisic could be set for a period on the sidelines with “torn calf fibers.”The American star missed out on Borussia Dortmund’s Champions League clash with Monaco on Wednesday, with the club announcing he had sustained the calf injury.The 20-year-old had played in four straight games for Dortmund, after missing two matches earlier in the season with muscle problems. Article continues below Editors’ Picks Man Utd ready to spend big on Sancho and Haaland in January Who is Marcus Thuram? Lilian’s son who is top of the Bundesliga with Borussia Monchengladbach Brazil, beware! Messi and Argentina out for revenge after Copa controversy Best player in MLS? Zlatan wasn’t even the best player in LA! In a statement on their website, the club also said that Pulisic will “undoubtedly” miss the club’s Bundesliga match against Augsburg on Saturday.Pulisic is now in doubt for the USA’s two upcoming friendlies against Colombia and Peru, set for October 11 and 16. The American has played just one game for his country in 2018, after making nine appearances in 2017 as the U.S. shockingly failed to qualify for the World Cup.Dortmund defeated Monaco 3-0 at Signal Iduna Park, making it two wins from two Champions League matches thus far.