Carter Kieboom and Nate Lowe both attracted plenty of attention when first called up to the majors — especially Kieboom, who appeared in my Five on the Verge in the weeks leading up to his promotion.

Each is back in the minors now, his first stint deemed a disappointment.

It's not as simple as that, obviously. The return of a higher-end player precipitated the demotion for each — Anthony Rendon in Kieboom's case and Austin Meadows in Lowe's. But each I think had a chance to stick if he made enough noise in the interim. 

So now what? They're still prospects, of course, and if they were among the ones most worth stashing prior to their call-ups, presumably they still are.

I'm not so sure, though. Irrational or not, now that they've tasted failure, the enthusiasm surrounding them won't be as high the next time around. The conversation in Kieboom's case will go from "he could be anything" to "he could be that guy who hit .128 with a 37 percent strikeout rate." The takeaway for anyone who invested in him the first time around will be "wow, what a letdown," especially since the concerns about his defense were more or less substantiated. Oh yes, it was bad.

Lowe, meanwhile, wasn't especially good, failing to hit a home run in eight games, but he did have a couple multi-hit efforts. His biggest issues are that first base is hardly a position of need right now and the Rays have a surplus of bats even when they lose someone to injury.

Long story short, I want to think about it a little more. I want to see how Kieboom and Lowe respond to their demotions and the chatter that accompanies them. I think it's fair to say, though, that stashing them is less of a priority now than it was prior to their initial call-ups, so if only for the sake of exploring new names, I'm for now leaving them out of my ...

Five on the verge

(These are the prospects most worth stashing in redraft leagues.)

Yordan Alvarez, OF, Astros

2018 minors: .293 BA (335 AB), 20 HR, 21 2B, .904 OPS, 42 BB, 92 K
2019 minors: .391 BA (110 AB), 14 HR, 11 2B, 1.353 OPS, 18 BB, 26 K

The speculation surrounding Alvarez has reached the point where it's landing on the desk of GM Jeff Luhnow, and his response was ... curiously contradictory. While he told the Houston Chronicle "it's pretty clear he can hit right now in the big leagues," Luhnow also said, "The same people who were clamoring for Kyle Tucker to come up because he was destroying AAA pitching are the same people now clamoring for Yordan Alvarez to come up.

"If [Alvarez] is coming up, he's coming up to play, and if he comes up and hits .210, that's not going to help our team. I need to make sure he's going to help our team."

So ... maybe it's not so clear Alvarez can hit right now in the big leagues? Muddying the waters are both Alvarez's defense (Luhnow thinks his best chance is in left field rather than first base) and the introduction of new baseballs across the Triple-A level, inflating numbers everywhere. But the Astros could free up the DH spot for Alvarez today, if they wanted to, and the 21-year-old has been the biggest of standouts even in that power-laden environment. I'm thinking this situation comes to a head sooner than later.

Jesus Luzardo, SP, Athletics

2018 minors: 10-5, 2.88 ERA, 1.09 WHIP, 109 1/3 IP, 30 BB, 129 K  
2019 spring: 0-0, 0.93 ERA, 1.03 WHIP, 9 2/3 IP, 4 BB, 15 K

Nothing new on Luzardo since he began throwing two weeks ago, which at the time put him on track to return in 4-6 weeks. So he should be getting pretty close to the start of a rehab assignment, though silence in these situations can be disquieting. His fastball/changeup combo earns the same sort of reviews Paddack's does (except Luzardo also has a quality breaking ball), and like Paddack, Luzardo appeared well on his way to securing a rotation spot this spring before straining his shoulder. We shouldn't have to wait so long once he's fully rehabilitated, in other words.

Zac Gallen, SP, Marlins

2018 minors: 8-9, 3.65 ERA, 1.47 WHIP, 133 1/3 IP, 48 BB, 136 K  
2019 spring: 5-0, 1.14 ERA, 0.57 WHIP, 47 1/3 IP, 8 BB, 55 K

All right, I'm ready to admit Gallen is worth stashing. He doesn't have a top prospect pedigree and doesn't earn particularly high marks for his stuff, but that stuff is playing up beautifully thanks to his pinpoint command — the result of a mechanical tweak made prior to the season. How beautifully? He keeps turning in seven-inning outings in which he allows only three hits with more than a strikeout per, which is especially impressive given the offensive explosion at Triple-A this year. His latest effort Wednesday was just two hits in seven innings. As desperate as we all for pitching, who wouldn't take a flier on him when he finally gets the call, which could happen the next time Sandy Alcantara disappoints?

Brendan Rodgers, SS, Rockies

2018 minors: .268 BA (426 AB), 17 HR, 27 2B, .790 OPS, 31 BB, 92 K
2019 minors: .339 BA (121 AB), 7 HR, 9 2B, 1.012 OPS, 14 BB, 20 K 

Ryan McMahon still hasn't gotten going at the major-league level. Garrett Hampson, meanwhile, looks completely overmatched. Second base, which once seemed like a wellspring of excitement and potential in the Rockies lineup is quickly becoming a sore spot, and it just so happens to be the position their top prospect is playing at Triple-A. Rodgers is long-awaited, having been drafted third overall in 2015, and his up-and-down minor-league career seems to be peaking at just the right time. A new, more patient approach has him batting .412 (28 for 68) with five homers in his past 17 games.

Cavan Biggio, 2B, Blue Jays

2018 minors: .252 BA (449 AB), 26 HR, 20 SB, .887 OPS, 100 BB, 148 K
2019 minors: .344 BA (96 AB), 6 HR, 4 SB, 1.048 OPS, 25 BB, 20 K  

Biggio has cooled off recently, batting .244 (10 for 41) in his past 13 games, but his strikeout and line-drive rates remain greatly improved, which gives him a much better chance of hitting for average than was assumed coming into the season. He's already well conditioned for a super utility role, having started at four different spots at Triple-A this year, and there isn't much need to play service-time games with him given that he's already 24. 

Five on the periphery

(These are some other prospects doing something of note.)

Keston Hiura, 2B, Brewers

2018 minors: .293 BA (485 AB), 13 HR, 34 2B, .821 OPS, 36 BB, 103 K
2019 minors: .336 BA (116 AB), 11 HR, 12 2B, 1.137 OPS, 11 BB, 35 K 

With the way Hiura is performing now at Triple-A San Antonio, it's getting to be put-up-or-shut-up time for Travis Shaw, who's established enough that the Brewers obviously don't want to do anything rash with him but ... it's been a pitiful display so far. And not in a way you could easily reduce to bad luck. Back when the Brewers signed Mike Moustakas to play second base, there was some concern it might block Hiura, who was considered close to major league-ready. Turns out the solution may be as simple as moving Moustakas back to his natural third base spot. 

Austin Riley, 3B, Braves

2018 minors: .294 BA (408 AB), 19 HR, 30 2B, .882 OPS, 37 BB, 129 K
2019 minors: .315 BA (124 AB), 12 HR, 10 2B, 1.074 OPS, 15 BB, 28 K  

Riley has had ups and downs throughout his climb to Triple-A Gwinnett, where he also played in 2018. He wasn't bad then, but things are going better for him this time around, mostly because his strikeout rate is no longer such a hindrance. Taking his entire minor-league career into account, that rate was never as bad as last year, and yet he remained one of the top prospects in a deep system because his power is great enough to overcome such a rate. Obviously, improved contact skills can only help. The way Riley has hit lately, homering 10 times in his past 13 games, he seems a more likely bet than Johan Camargo to take over at third base if Josh Donaldson were to suffer a long-term injury. And hey, there's also talk of the Braves giving him some looks in the outfield.

Mitchell White, SP, Dodgers

2018 minors: 6-7, 4.53 ERA, 1.41 WHIP, 105 1/3 IP, 34 BB, 88 K  
2019 minors: 1-0, 1.85 ERA, 0.78 WHIP, 24 1/3 IP, 6 BB, 30 K

White was one of the prospects whose stock dipped the most last year as he struggled to find any consistency with his delivery and release point after losing the first month to injury. He looks like he's back on track this year, though. Like Walker Buehler, White has two breaking balls — a slider and curveball — that show plus potential, and he has been putting in extra work on both in his side sessions. Over his past two starts, he has allowed a total of three hits with 16 strikeouts compared to just one walk in 11 2/3 innings.

Sam Huff, C, Rangers

2018 minors: .241 BA (415 AB), 18 HR, 9 SB, .731 OPS, 23. BB, 140 K
2019 minors: .333 BA (108 AB), 15 HR, 4 SB, 1.165 OPS, 6 BB, 37 K  

Huff has big-time power, just like the numbers show, and of course the threshold to meet offensively is much lower at catcher. But the threshold to meet defensively is much higher, and seeing as Huff is already spending half his time at DH as a 21-year-old in low A-ball, he may not be long for the position. Especially given the high strikeout rate, a Peter O'Brien-like trajectory seems likely here, but it's possible Huff's one standout tool is enough to carry him.

Jordan Balazovic, SP, Twins

2018 minors: 7-3, 3.94 ERA, 1.17 WHIP, 61 2/3 IP, 18 BB, 78 K  
2019 minors: 3-1, 1.63 ERA, 0.69 WHIP, 27 2/3 IP, 4 BB, 43 K   

Balazovic didn't get much prospect love last year despite having 11.4 strikeout per nine innings. That rate is up to 14.0 this year. He just debuted for high Class A Fort Myers Sunday, striking out 10 over seven perfect innings. A new slider grip seems to have unlocked a genuine swing-and-miss pitch, and his control is top-notch as well. He has issued just four walks between five starts this year. Obviously, he still has a climb ahead of him, but the 20-year-old deserves some looks in deeper dynasty leagues.