Knebel, 29, is entering his final year of arbitration eligibility and will earn approximately $5 million in 2021, according to MLB Trade Rumors' projections.
Knebel missed the entirety of the 2019 campaign while recovering from Tommy John surgery.
He posted a 6.08 ERA and 6.64 FIP over 13 1/3 innings in 2020 and was seen as a likely non-tender candidate ahead of Wednesday's deadline.
In the two years prior to his surgery, Knebel was one of the top closers in baseball. He authored a 2.54 ERA and 2.74 FIP to go along with 55 saves over 131 1/3 innings in 2017 and 2018.