But one of the beautiful things about baseball is that there are no sure things. Nor are there any limits to how far a player can go if he combines skills with a belief in himself.
So while Appel, Foltynewicz and other prospects are pitching their way to join an Astros team that figures to be led by shortstop Carlos Correa and outfielder George Springer a couple years from now, the guys taking their turns for Bo Porter in Houston are working to show that they have the stuff to stick around.
"We're pretty talented," said 26-year-old left-hander Dallas Keuchel, who on Tuesday night beat the Rangers, 8-0. "We're Major League baseball players, no different than other guys, like the Yankees and Red Sox and those guys. They were in the position we're in at one point. It's all about getting your feet on the ground and moving. I think we're doing a great job."
Veteran Scott Feldman, signed to a three-year contract to provide both leadership and stability, is doing his part. But it is the other guys in the rotation -- Keuchel, Jarred Cosart, Collin McHugh and Brad Peacock -- who have gotten rolling as a unit, giving Porter hope that 2014 won't be the same type of ordeal as 2013 for the Astros.
"I definitely think they're feeding off each other," Porter said. "We have a good group of five guys who are close knit. They talk to each other on the bench, they watch each other's starts. I think Scott Feldman is leading that charge -- understanding how you can help each other game in and game out, and I think it's really paying dividends for all these guys."
After ranking 13th in the American League with a 4.72 ERA last season, Houston's rotation has improved to eighth at 4.19. The starters have turned in six quality starts in the last seven games, including ones by Keuchel against the Rangers and Tigers.
Keuchel was masterful against Texas on Tuesday, throwing a seven-hit, walk-free complete game. He bounced between the rotation and the bullpen last season and didn't assure himself of a spot in the rotation until late in Spring Training, but he is about to find himself in the middle of something new -- All-Star Game speculation.
Catcher Jason Castro and second baseman Jose Altuve have represented the Astros in the last two All-Star Games, and Altuve seems the most likely to go this season. But Feldman (2-1, 1.93 ERA in five starts entering Wednesday's game against the Rangers) and Keuchel are putting themselves in position to receive some consideration.
Like the Cubs' Travis Wood a year ago, Keuchel is getting results by throwing strikes and getting hitters to beat the ball into the ground. There was nothing especially dramatic about the job he did against Prince Fielder and the Rangers, but he was efficient, and when he walked outside to his car, he was 4-2 with a 3.06 ERA.
"This has been trending upwards for awhile," Porter said. "He's been throwing the ball pretty good for a long time now."
Keuchel has always been a good pitcher. He led his Bishop Kelley High team to a state title in Oklahoma, then did well enough at the University of Arkansas to get selected in the seventh round of the 2009 First-Year Player Draft. But Keuchel is not a guy who lights up radar guns, so he has had to prove himself through his results.
"If I throw strikes, I'm good," Keuchel said. "If I don't, I'm not very good. I'd rather throw strikes and be good."
Porter has seen Keuchel develop into a polished pitcher over the last two seasons.
"I think when you're able to plus and minus your fastball and have the type of command that Dallas has, you can pitch," Porter said. "He's able to cut the ball in to the righties, sink it away from righties, which runs it in on lefties. He has confidence to throw his breaking ball and his changeup in any count.
"You look at what he was able to do tonight, the most impressive thing to me was that regardless what the score was, 8-0, he just kept pitching. [He was throwing] 3-1 changeups, 2-0 breaking balls. He didn't just say, 'We're up 8-0, let's just try to get through this.' That's complete maturation of not losing focus and continuing to pitch regardless of the situation."
A lot of guys have had long careers throwing exactly the way Keuchel did. The Astros will have found a fixture if he can keep this up.