Forward Thomas Hertl has left the San Jose Sharks road trip and returned to California for an MRI, CSN Bay Area reported Friday.
Hertl seemed to injure his right knee in the second period of a 3-2 loss at the St. Louis Blues on Thursday.
"Any time you're sending a guy back early on a trip to get looked at there's concern, but you look around the League, everyone is dealing with injuries," coach Peter DeBoer told the website Friday.
Hertl had four goals and five assists (nine points) in 17 games this season. Last season ended in Game 2 of the Stanley Cup Final against the Pittsburgh Penguins when he injured the same knee.
"He's been through a lot for a young guy," DeBoer said. "He was playing great, arguably been one of our best players through the first  games and after a summer of rehab. You feel for him."
Forward Melker Karlsson could return to the lineup Saturday against the Arizona Coyotes (8 p.m. ET; FSN-A, CSN-CA, NHL.TV) in the final game of the road trip. He missed two games with a foot injury after blocking a shot against the Tampa Bay Lightning on Nov. 12.