The Orioles are running out five and six rookies for some games. The Cardinals are relying on three rookie relievers to close out games down the stretch. The Mariners have ridden a rookie closer into contention.
Welcome to baseball's new normal.
We already knew young players were being fast-tracked through the Minors, that teams were trusting that their talent would win out over experience. That's going to be true in these final weeks, with virtually every contender using rookies in important spots.
Let's look at possibly the 10 most important rookies in the final six weeks of this season:
1. Edwin Díaz, RP, Mariners
The Mariners are 12-4 since turning the ninth inning over to the 22-year-old right-hander with the 97-mph fastball. Diaz has converted eight straight save chances, and his emergence has allowed manager Scott Servias to align the arms in front of him. Seattle's bullpen has a 2.29 ERA, the second best in the Majors, since the switch, and the Mariners are three games behind the Orioles and the Red Sox in the race for an AL Wild Card berth.
2. Michael Fulmer, SP, Tigers
Fulmer can begin clearing trophy space for the AL Rookie of the Year Award in a season in which he's leading the AL with a 2.25 ERA and has helped make Detroit's rotation -- that rotation with all the questions -- one of the best in the game. The Tigers' starters have a 2.86 ERA this month, trailing only the Cubs (1.49) and Red Sox (2.56). Fulmer, 23, has become a machine, with Detroit winning 13 of his past 15 starts thanks to a 1.43 ERA. He has allowed one or zero runs in nine of those 15 starts and more than two runs just twice. Fulmer's workload is a concern. His 135 1/3 innings (including three Minor League starts) are a career high, and the Tigers will attempt to give him an extra day and hope he's honest with them about how he's feeling. After Fulmer's complete-game shutout last Sunday, manager Brad Ausmus said, "He's not making it easy for us."

3. Corey Seager, SS, Dodgers
Seager is 22 years old and is probably already one of the 10 best players in baseball. He has pretty much clinched the NL Rookie of the Year Award and also should earn NL Most Valuable Player Award votes. Seager has 21 home runs and an .893 OPS to go with defensive work that might be the best in the NL for shortstops not named Brandon Crawford. The Dodgers climbed atop the NL West for the first time since mid-May this week, and Seager is a huge reason. The Dodgers have been hit hard by injuries and have an uncertain rotation. But Seager has elevated them dramatically.
4. Jameson Taillon, SP, Pirates
Taillon has been at the center of a remade starting rotation that has helped the Pirates remain in contention for an NL Wild Card berth. He has been so consistent with both his 96-mph fastball and ability to command the strike zone (nine walks, 52 strikeouts in 66 innings) that it's impossible to believe he's just 24 years old and missed the past two seasons with injuries. The Bucs are 8-3 in Taillon's 11 starts, and he has delivered nine quality starts. He's one of the reasons the Pirates believe a third straight postseason berth is doable.
5. Trea Turner, 2B/OF, Nationals
Turner is going to be one of baseball's 10 best shortstops in the next couple of years. For now, manager Dusty Baker is using him at second base and center field to get his bat at the top of his batting order. Turner's .313 batting average helped the Nationals open up a 9 1/2-game lead in the NL East.

6. Seunghwan Oh, RP, Cardinals
Oh is a rookie in name only, being 34 years old and having collected 357 saves during 11 seasons in Japan and Korea. What Cardinals fans know is that he has combined with two other rookies to stabilize a bullpen that has been an area of concern all season. Down the stretch, manager Mike Matheny will lean on three rookies who've been outstanding -- not just Oh, but also Alex Reyes and Matt Bowman as the Cards attempt to go to the playoffs for a sixth straight season.
7. Gary Sánchez, C, Yankees
The Yankees have turned a page and opened up their roster to an influx of young guys the next two seasons. Sanchez, 23, is hitting .360 and may be the best of the kids, but Aaron Judge and Tyler Austin are also off to good starts. These were big-picture decisions for the franchise with 2017 and beyond in mind, but the Yanks are six games out in the race for the second AL Wild Card berth.
8. Dylan Bundy, SP, Orioles
Bundy has had a long, winding and frustrating path to this point since the Orioles made him the fourth overall pick of the 2011 Draft. Manager Buck Showalter inserted him in the starting rotation after the All-Star break, and he has been excellent five times and struggled twice. Bundy's 75 innings are 51 more than he pitched in 2015 as he recovered from surgery, and the O's are going to monitor his workload carefully the rest of the way.
9. Nomar Mazara, OF, Rangers
Mazara is going to be high on a lot of AL Rookie of the Year Award ballots for a season in which he has been a consistent producer on a team headed to the postseason for the fifth time in seven seasons. His .282 batting average and .754 OPS have made him invaluable for a team that had its regular right fielder, Shin-Soo Choo, for only 45 games.

10. Yulieski Gurriel, 3B, Astros
Gurriel has not even played a Major League game yet, but the Astros are hoping he can join them in the next few days and add some pop to an offense that is 22nd in runs this month. With Houston 6 1/2 games out of the race for the second AL Wild Card, its margin for error is almost nothing.