Following a pair of scoreless innings against the Cleveland Indians over the weekend, his Royals record now stands at 27 straight appearances, covering 26.2 innings. Davis has pitched exactly one inning in all but one of those games, having thrown two-thirds of a frame July 31 against the Minnesota Twins.
Sporting a 0.75 ERA, 0.83 WHIP and 90:21 K:BB through 60.1 innings this season, Davis is having one of the finest seasons for a relief pitcher in major-league history. He didn't allow an extra-base hit until his 44th appearance of the year, which came in the aforementioned game against the Twins on July 31.
Having still allowed just two extra-base hits (both doubles) all season, Davis has held opponents to a minuscule .010 isolated slugging (ISO) mark, which is calculated by slugging percentage (.149) minus batting average (.139).
According to Baseball-Reference's play index (via ESPN.com), only one qualified pitcher since 1957 has held his opponents to a lower ISO over the course of a full season. Doing the honors was Frank Williams, who gave up just one extra-base hit over 52.1 innings for the San Francisco Giants in 1986, good for a .006 opponents' ISO.
Among pitchers who have thrown at least 40 innings, Davis leads the majors in opponents' slugging percentage (.139), while ranking second in opponents' batting average (.139) and ninth in opponents' on-base percentage (.227). His 2.5 WAR ranks third, behind only New York Yankees rookie reliever Dellin Betances' 2.7 and Tampa Bay Rays closer Jake McGee's 2.6.