Kendall, a three-time National League All-Star, has had two shoulder surgeries since he last played on Aug. 30, 2010, with Kansas City. He has been working out with the Royals since spring training.
Kendall, a career .288 hitter, ranks fifth all-time with 2,025 games caught.
Later Thursday, the Royals optioned Vin Mazzaro to Triple-A Omaha.
Mazzaro gave up three runs and four hits in 2 1/3 innings Tuesday.
Mazzaro is 3-3 with a 6.12 ERA in three stints with the Royals this season, allowing 44 hits and walking 12 in 32 1-3 innings.
Information from The Associated Press was used in this report.