To be clear, these lists only include players still in the Kansas City system or ones not with season-ending injuries. This affects players such as Aroldis Chapman, Kris Bubic, and more. All statistics are courtesy of FanGraphs.
Royals Starters (minimum three starts)
1. Ryan Yarbrough - 4.26
Ryan Yarbrough is no one's favorite Royals pitcher, but the 31-year-old veteran produces in the starting role. He started in his last three appearances from April 26 to May 7. He struggled against the Baltimore Orioles on May 2, giving up five earned runs in 3 2/3 innings. Outside of that though, he held opponents to two earned runs over 9 2/3 innings with one walk to four strikeouts. Not bad, but far from a sure thing in the starting rotation. Let's hope he returns to Kansas City soon, after his scary injury.
2. Brady Singer - 4.36
Brady Singer was fans' choice to be the team ace, but a terrible first two months of the season colled those expectations. He had six starts where he gave up five or more earned runs in April and May, hardly what is expected of a team's best starter. His stats have improved since June began, with 25 strikeouts and 11 walks across six starts. 12 runs in 35 1/3 innings make for a great 3.06 ERA and 3.54 FIP. But, if Singer wants to put the season's start behind him, his solid outings will have to continue through the summer.
3. Zack Greinke - 4.64
Here is a prime example of the difference between ERA and FIP. Zack Greinke's ERA sits at 5.15 while his 4.64 FIP is significantly lower. Not only do the Royals fail with providing him run support, but they also fail with backing him up in the field apparently. His FIP would be the third-highest in his career if the season ended today. Greinke is still a valuable member of the rotation, especially in Kauffman Stadium. But his current FIP is a far cry from the elite metrics of his first stint in Kansas City.
4. Daniel Lynch - 4.83
Daniel Lynch's FIP has been a roller coaster this season since he made his debut on May 28. A seven-run outing against the Cincinnati Redis is mostly to blame for that. Lynch's FIP is not tideal, mostly due to the four home runs he gave up on June 14, coupled with his nearly equal number of walks and strikes out his last three starts. Lynch has not been an overpowering pitcher this season, but rather the result of good luck and a better defense behind him.
5. Jordan Lyles - 5.60
Yes, we all know the saga that is Jordan Lyles in a Royals uniform. He is setting all sorts of history in the wrong way while failing to keep Kansas City competitive in ball games. He is at least averaging 5 2/3 innings per start, but those are rarely productive outings. His FIP in June came out to 4.02, closer to what you want for an average starter. But, his 5.40 ERA in that same span negates and steps forward Lyles may be making this summer.
The Royals starting staff's FIP comes out to 4.87, good for the fifth-worst in MLB. The Reds are the only playoff-contending team with a worse FIP than the Royals. It is worth noting that Kansas City's starting staff's 5.41 ERA is significantly higher than their FIP. The .54 gap is not massive at an initial glance but it is the fourth biggest gap in all of MLB. That gap lies solely on the sporadic and disappointing Royals defense this season. I know that Bobby Witt Jr. and Maikel Garcia likely make up the best left-infield defense in the AL Central, but the remaining defenders do not make for sub-par play elsewhere.