Gray has not pitched in eight days because of the schedule. The Yankees had days off Monday and Thursday, were rained out Wednesday in Washington after getting Tuesday's game suspended following the top of the sixth inning.
The teams split the first two games of the series.
After Kansas City opened the series with a 5-2 win, the Yankees hit a season-high five homers in an 8-3 win on Saturday.
Rookie Gleyber Torres hit a three-run homer and Gary Sanchez tied a career high with four hits, including two solo blasts. In addition, Giancarlo Stanton had a solo shot and Aaron Hicks added his second inside-the-park homer of the season.
Gray has struggled this season, going 2-3 with a 6.39 ERA in his first eight starts.
In his previous start on May 11 against Oakland, Gray allowed nine hits, including a pair of home runs, and five earned runs in five innings, while walking three and striking out two in a 10-5 loss.
"I felt good," Gray said after his last start. "I just couldn't put it together. I feel like my stuff was pretty good but at the end of the day they put five runs across the board in five innings, when you do that it's going to be tough to win those games."
Gray has pitched five or less innings in five of his starts. He has posted only one victory since April 7 and is 6-10 with a 4.70 ERA in 19 starts since being acquired from the Athletics in a trade on July 31.
Gray is 1-2 with a 2.77 in four career starts against the Royals. He is 0-1 with a 4.15 ERA in two starts in Kansas City.
Abraham Almonte is 4-for-8 off Gray, while Mike Moustakas is 2-for-12, .167, Ryan Goins 1-for-10, .100, and Alex Gordon, 2-for-11, .182. No current Royal has homered off Gray.
The Royals will counter with left-hander Eric Skoglund, who is 1-3 with a 5.58 ERA in seven starts.
Skoglund lost his previous start on Monday to the Tampa Bay Rays 2-1. He worked a career-high 7 2/3 innings and for the first time in 12 career starts did not walk a hitter.
Skoglund is 1-3 with a 4.88 ERA in four home starts this season.
Skoglund has never faced the Yankees. He is 0-2 with a 4.74 ERA in three starts this season against AL East clubs.
Shortstop Didi Gregorius, who is in a 1-for-45 slump to drop his average to .248, and outfielder Brett Gardner, who is hitting .182 with 11 strikeouts in 33 at-bats with no extra-base hits against left-handers, were held out of Yankees lineup Saturday.
Manager Aaron Boone wanted to stack the lineup with righties against Royals left-hander Danny Duffy, plus give Gregorius a mental break.
I do think it's good for him to get a little bit of a break and I think matchup-wise this is the one that makes the most sense," Boone said.
Gregorius, who was the American League player of the month in April when he slugged .739 with 10 home runs, six doubles and 30 RBIs in 21 games, will be back in the lineup Sunday.
The Royals placed infielder Cheslor Cuthbert on the 10-day disabled list with a lower back strain and made it retroactive to Wednesday.
They recalled switch-hitting infielder Ramon Torres, who was hitting .229 in 39 games with Triple-A Omaha. He made his big-league debut last year, hitting .243 in 33 games with three doubles and scored nine runs.
"We've got games coming up Monday in St. Louis in a National League city and I need someone healthy," Royals manager Ned Yost said. "I've got a short bench as it is, and I've got to be able to use it. Cheslor's situation isn't that bad and if we weren't going to a National League city, we probably don't DL him."