Jerick McKinnon, who missed last season after tearing his ACL, will undergo knee surgery.
The 49ers placed running back Jerick McKinnon on the injured reserve with a knee injury.
McKinnon will be out the entire 2019 season, and 49ers general manager John Lynch said the veteran will require knee surgery.
"He needed to undergo another procedure where being available in eight weeks wasn't an option," Lynch said, per Bay Area News Group's Cam Inman. "We're hopeful for Jerick that this one will be successful. There were some mechanical issues that did not allow him to play."
NFL Network's Ian Rapoport reported on Friday that McKinnon "had a bit of a flare up" recently.
The 27-year-old running back missed all of 2018 after tearing his right ACL before the start the season, his first with San Francisco. McKinnon struggled with setbacks throughout this year's training camp and was placed on the physically unable to perform list. After being activated on Aug. 6, he was sidelined for three weeks after another issue. However, his struggles continued during practice this week.
McKinnon hinted at his injury struggles on social media on Friday.
"No matter the circumstances I'll never fold," he said.
No matter the circumstances I’ll never fold— Jerick Mckinnon (@JetMckinnon1) August 30, 2019
McKinnon played the first four seasons of his career with the Vikings, who selected him in the third round of the 2014 draft. He signed a four-year, $30 million deal with the 49ers as a free agent in March 2018. His $3.7 million salary for 2019 is fully guaranteed. He made $12.5 million in his first year with the 49ers, including an $8 million signing bonus.