Johnny Cueto is in trouble. What kind of trouble, we don’t know yet, but on Sunday he pitched three innings, giving up five runs and nine baserunners against the Chicago White Sox, and absorbed another loss.

This makes it four consecutive losses for Cueto. Where before he had a 2.46 ERA and 0.93 WHIP in his 23 turns for the Cincinnati Reds and Kansas City Royals, in these four beatings Cueto has allowed 22 runs in 20 innings with a 2.00 WHIP.

It’s the stuff of deep concern for the adopted ace of the team that picked Cueto up at the trade deadline. And it’s something that forces the Royals to determine whether it’s something they can fix or something they have to work around by the time they reach the postseason.

Dig into the games themselves, and you might think Cueto isn’t pitching radically differently in these past four starts. One easy (read: lazy) way of addressing Cueto’s struggles would be to blame it on his defense because his BABIP in these four turns is .446, versus .243 before. And while his K/9 was 7.9 in his first 23 starts this season, he’s whiffed 7.7 in these past four starts in which he has taken a beating. And his K/BB ratio has gone up, from 4.3 to 5.7. Usually those might be seen as good things. But in this case it seems to mean that Cueto is getting creamed by the people he isn’t fooling.

If you dig into Cueto’s Pitch F/X data, his fastball still is sitting around 92-93 mph, the same before and during his slump. You’ll also learn that he’s throwing a few more cutters (23.5 percent of the time, up from 17.1 percent) and fewer sliders (down to 8.4 percent from 12.4 percent). It’s interesting that he’s also getting a bit less spin on those sliders (down to 537 rpm from 580), and that he’s locating them less effectively and further away from the strike zone, throwing strikes just 35 percent of the time after putting them in the zone 58 percent of the time, and understandably getting fewer called and swinging strikes as a result.

There are mechanical issues involved as well. Before Sunday’s beating, Lee Judge reported for the Kansas City Star a few days back that pitching coach Dave Eiland said Cueto’s front shoulder is flying open, meaning he delivers late while flattening out his fastball, cutter and change.

Johnny Cueto, who had another poor start Sunday, has allowed 22 runs in 20 innings with a WHIP of 2.00 over his last four outings. Peter Aiken/USA TODAY Sports

Eiland and Cueto thought that was a fixable work in progress, but Sunday’s beating doesn’t reveal anything of the sort. The key result these days is that Cueto is getting creamed by righties and lefties alike, as both are up between 400-500 OPS points during his grim four-game stretch. Whether it’s mechanical or health-related, and something that rest or evaluation might resolve, it’s an execution issue that the Royals can ill afford from the guy they thought they could safely tab to start Game 1 in any postseason series.

They still have four weeks to sort it out, of course, and they have the advantage of a 12-game lead in the AL Central and little at stake beyond securing home-field advantage through the LDS and LCS rounds.

If Cueto can’t be fixed in the intervening time, where does that leave the Royals? The good news is that Yordano Ventura has thrown five straight quality starts for five Royals wins, posting a 1.13 ERA with a 43/13 K/BB ratio in 32 IPs. If that continues, he may well be their top gun, with Edinson Volquez as their obvious alternative chugging along as the Royals' most reliable starter.

But even after bumping those two up a peg, whoever gets tabbed as the No. 3 is probably going to have to start two games in an championship series or World Series, and somebody else will get that once-a-series assignment as the No. 4. Manager Ned Yost will have to select from among veterans Chris Young and Kris Medlen from the right side, and Danny Duffy from the left. And perhaps in an extreme situation, Jeremy Guthrie is still hanging around.

It isn’t a great group to choose from. Medlen is perhaps still rounding into shape since his return from surgery, but he hasn’t looked all that good in his three turns, so any decision may be simpler still if he doesn’t improve. Young, a towering soft-tosser, struggles after his first time through an order, seeing his opponent’s OPS leap from .569 to north of .800. He also rarely gets out of the sixth inning while getting beaten on a bit by lefties. Duffy might be the most consistent and durable of the three, but since taking a step forward in July and August, rattling off six quality starts in eight turns, he has none in his past four.

Yost simply might end up having to play matchup games in the rotation as much as he would in the bullpen. If the Royals face the Rangers in the division series, for instance, a soft-tossing righty such as Young might have value, considering Texas’ troubles with off-speed pitches, ranking just 13th in the league in OPS against the softer stuff. The Rangers, Twins and Orioles all rank in the bottom half of the league against lefties -- enter Duffy. If somehow the Royals end up facing the Twins, Minnesota struggles against hard-throwing righties (ranking last in OPS), so Ventura becomes an obvious choice to favor up front. But the stronger lineups of the Blue Jays, Yankees or Astros present no easy answers.

Which is why they might have to break from established roles. But does Yost have it in him to use a quick hook, to perhaps mimic the benefit of getting into his bullpen early the way Tony La Russa did to win it all with the Cardinals in 2011? Maybe Medlen or Young can play middle-relief hero, much like Yusmeiro Petit did last year or Tim Lincecum in 2012, and with Francisco Morales and Ryan Madson added to the Royals’ great late-game trio, depth in relief is still one thing the team should be able to count on. But somebody still will have to start the games.

It’s mulling these options that might understandably frighten Royals fans looking ahead to October, and leave them hoping that Cueto gets his issues ironed out. Cueto was supposed to bring certainty, but now there’s just hope that he can be what he’s supposed to be.

Christina Kahrl writes about MLB for ESPN. You can follow her on Twitter.