"You've got a chance to win every time out -- what more can you ask for, right?" said a scout from an American League Central rival.
Those three right-handers will mesh with Jeremy Guthrie, who was re-signed as a free agent, and a to-be-determined fifth starter, probably Bruce Chen or Luke Hochevar.
"If they get just reasonable expectations from the three that they traded for, coupled with the bullpen, I think the Royals are in much, much better shape in the 2013 season," another scout said.
They came at a high cost. To pry Shields and Davis from the Rays, the Royals gave up top hitting prospect Wil Myers and top pitching prospect Jake Odorizzi and two other highly-regarded Minor Leaguers. For Santana, they gave up a marginal pitching prospect to the Angels, but took on $12 million in salary for one year.
"They are three different types of pitchers," said Rangers third baseman Adrian Beltre. "Shields eats up innings and has a good sinker for a fastball and a good curve, but he has that really good changeup. It is one of the best changeups, and that's the pitch that really makes him tough.
"Davis has really good life on his fastball. When he locates it, he can be really tough. He also has a really good slider and a breaking pitch. He's been kind of back and forth the last few years.
"Santana has good life on his fastball, and his slider has really good bite. For him, it all depends on how he is locating that day. Sometimes he doesn't have the movement that he needs, and that's when he gets into trouble. The biggest thing is he can be really inconsistent."
Beltre should know. He's done fine against Davis (4-for-10, .400) but not so good against Shields (9-for-41, .220, with 18 strikeouts) or Santana (12-for-54, .222, but with 15 RBIs).
The rave about Shields centers around his changeup.
"He's got an outstanding changeup -- one of the best changeups in baseball that allows him to be equally successful versus right-handed and left-handed hitters," a scout said.
Shields is the only Major League pitcher to throw his changeup at least 1,000 times last season, according to STATS LLC. He threw it 28.8 percent of the time. Opposing hitters swung and missed it 36.7 percent of the time he threw it. That was the fifth-highest swing-and-miss ratio for any pitch thrown at least 1,000 times last season.
"He'll throw it at any time," said the Yankees' Curtis Granderson about Shields' changeup. "There's no falling into patterns, like, 'Two strikes, I'm going to throw it.' He'll throw it 0-1, he'll throw it 0-0, he'll throw it 2-0, he'll throw it 3-1. He's good. I feel like every time we've faced him in general, outside of him just being amped up to play the Yankees, he's obviously good, and when he comes against us, it's never been a high-scoring affair. It seems like no one on our team seems to hit him very well."
Scouts rate Shields as having a plus-fastball, a little harder than it used to be, with the stamina to consistently go deep into games, and a strong pickoff move.
"He's probably got the quickest move of any right-hander in the game today," one of them said. "It's lightning quick. You've got to be really careful. You get off too far, he'll pick you off."
Shields' competitive toughness is one of his hallmarks.
"He's just a gamer," said the Orioles' Nick Markakis, who has a .303 (20-for-66) mark against Shields. "You know you've got a battle on your hands for seven to nine innings with him. He just locates the ball. He puts the ball where he wants. He's got a putout pitch with that good changeup. He keeps hitters off-balance all day."
The change in environment could be a plus for Shields, according to one scout.
"Especially going into a big ballpark and pitching outdoors, I think is going to be a positive sign for the Royals," he said. "Another thing is, he wants the ball, he's not afraid to take the ball. There's something to be said for a guy who's a top-of-the-rotation starter who's willing to take the ball and doesn't back down from a challenge. That's James Shields."
Santana had an off year in 2012, but in the past, he's had a pattern of bouncing back the next season. He has extra incentive this year as he approaches free agency next winter.
"Santana is a little bit of an enigma, because he's got very good stuff -- an above-average fastball, a breaking ball that's in between a slider and a curveball, and a changeup," a scout said. "He had trouble in early innings last year, he had trouble with the home run, principally because he was up in the zone a lot. But up to last year, he was a very durable starter. He did have some physical issues, but he's a good pitcher that certainly has some upside left."
There's been no evidence of any physical issues for Santana, and he and the other starters whizzed through their first (and in Davis' case, second) Cactus League starts leading up to Monday's off-day.
"The down year probably helped him mature as a pitcher, so it's something that's probably a positive right now," one scout said.
"When healthy, that guy can be as dominating as any guy in baseball." Markakis said. "It's fun facing those type of guys, though. You know you're going to have a battle. You know it's a challenge. They're veteran guys. They know how to pitch. They've been around a while, and aside from having good stuff, they have a good presence up there."
Davis pitched exclusively in relief last year only because the Rays' starting rotation was so deep, but his background is as a starter.
"He has the best pure stuff of the three," a scout said. "He has tremendous upside -- he's got an above-average fastball, a breaking ball, developing changeup, and it's just a question of keeping his pitch count down and his walks totals down.
"But I really like Wade Davis. I'd like to see him get a little more movement on his fastball than I saw last year, but he's a power pitcher, where Shields is a command-and-feel-type of pitcher. Davis is pure arm strength who has really yet to gain consistency with his location because of the fact he hasn't been in a consistent role."
Compared to Shields (217 starts) and Santana (233 starts), Davis is a relative beginner with 64 starts in the Majors.
"He's gotten a lot better from the first time I faced him," Markakis said. "He's just learning how to pitch. He's got good stuff. He's got a good fastball. He's mixing in a cutter, and he's got a good curveball. Tampa's always had good young pitching. Anytime you face a guy from Tampa, you know you're going to have a battle."
Or now, if things go the way the Royals hope, anytime you face a guy from Kansas City.