McKennie was making the first appearance of 2018 for Schalke 04, coming off the bench in the 63rd minute for Bayern Munich-bound Leon Goretzka in central midfield.
Twenty minutes later, he injured his knee in a challenge with Hannover's Felix Klaus. McKennie immediately clutched his knee, tried to continue but was taken out of the game.
Less than a year after he signed from FC Dallas academy program, McKennie was promoted to the Schalke 04 first team and made his debut on the last day of the 2017-18 season.
He has played 14 goals -- with nine starts -- for Schalke this season. Schalke 04 is one of four teams tied for second place with 31 points, 16 points behind Bayern Munich.