Keller is unable to travel with the Royals to Canada for the four-game series against the Blue Jays due to his vaccination status, so he'll be placed on the restricted list Thursday ahead of the series opener, Anne Rogers of MLB.com reports.
Keller lined up to make one final start before the All-Star break this weekend, but he won't be able to join the team in Toronto. The 27-year-old finished the first half with a 3.96 ERA, 1.27 WHIP and 67:32 K:BB across 97.2 innings, and he should take the mound in one of Kansas City's first couple games out of the break.