Watkins left last week's game against the Los Angeles Chargers early with a head injury and did not return.
"Sammy got a hit to the head that I thought was very questionable," Reid said postgame Sunday, according to the Kansas City Star's Herbie Teope.
Watkins had seven receptions for 82 yards and a score in Week 1 but recorded just one catch for 11 yards in Week 2 before his injury. The 27-year-old wideout has tallied 4,337 yards and 32 touchdowns during his career.
The Chiefs' next game is on Monday against the Baltimore Ravens.