The Astros have made seven straight American League Championship Series appearances, setting an AL record in the process. But earlier this season, it looked like Houston's incredible run was poised to come to an unceremonious end.

When the Astros awoke on June 19, they were 10 games behind the Mariners in the AL West with a 33-40 record. After their loss to the White Sox on June 18, FanGraphs gave them just a 29.3% chance of reaching the postseason.

Houston’s starting rotation, typically so reliable during its historic streak, deserved a lot of the blame for its rough start. Through June 18, Astros starters had MLB’s seventh-worst ERA at 4.53 and were worth just 3.5 WAR.

The club was also dealing with a serious lack of depth at the time. Justin Verlander went on the injured list with a neck issue on June 18, joining Cristian Javier, Lance McCullers Jr., J.P. France, José Urquidy and Luis Garcia among Astros starters on the IL.

Nearly three months later, though, the Astros are not only leading the AL West but also might have the best rotation of any AL team currently in possession of a playoff spot.

Entering Monday, these were Houston’s starting pitching ranks across all of MLB since the All-Star break:

• First in ERA (3.28)
• First in FIP (3.40)
• First in WAR (5.8)
• Tied for first in opponents’ batting average (.209)
• Third in strikeout rate (28.2%)

The Astros have managed to post those numbers despite Verlander's troubling return from the injured list. The three-time Cy Young Award winner has given up 19 runs over 17 2/3 innings in four starts since coming off the IL, and his playoff rotation spot is in jeopardy after he was hit hard by the D-backs on Sunday.

Still, the club's starting staff appears to be in good shape with October looming. Here are three reasons why the Astros' rotation has made such a dramatic turnaround and looks primed for success in the playoffs.

All stats below are through Sunday.

Framber Valdez started pitching like an ace again

After earning All-Star selections and Cy Young votes in each of the past two seasons, Valdez dealt with some inconsistency early in the year, allowing five or more runs in three of his first 11 starts and recording a 3.99 ERA in that span.

But Valdez has turned it on over his past 14 starts, recording a 2.21 ERA with 102 strikeouts and a .528 OPS allowed across 89 2/3 innings.

He’s been especially dominant since the calendar flipped to August, posting a 1.32 ERA over six starts, including a scoreless gem against the D-backs -- MLB’s highest-scoring offense -- on Friday night.

Valdez has dialed up his curveball usage during his hot streak, throwing it 34.8% of the time over his past 14 starts (26.2% in his first 12 starts).

In that span, Valdez’s curveball has limited opponents to a .099 batting average and a .144 slugging percentage, generating 58 strikeouts in 122 plate appearances.

It’s been the second-most valuable pitch in the Majors since June 18 in terms of run value (+14), which takes the result of every pitch thrown and measures its impact on run scoring.

Hunter Brown has broken out

After bursting onto the scene with a 0.89 ERA over 20 1/3 innings late in 2022, Brown struggled as a rookie last year, pitching to a 5.09 ERA over 31 appearances (29 starts). It was more of the same in the early stages of 2024, with Brown notching a 7.71 ERA in his first nine games (eight starts).

However, a tweak to Brown’s repertoire has helped everything fall into place for the 26-year-old righty, who has recorded a 2.02 ERA, a 2.99 FIP and a 120-to-34 K/BB ratio across 115 2/3 innings in his past 19 starts.

Starting in May, Brown began to incorporate a sinker into his pitch mix while throwing fewer four-seam fastballs. He also started going up the ladder with his four-seamer more often. Over his past 19 starts, 64.4% of Brown’s four-seamers have been elevated, compared to 58.4% in his first nine outings.

With those changes, Brown’s four-seamer has gone from being one of the worst of its kind in baseball to one of the best.

Brown’s four-seamer through May 21:

• .325 BA / .584 SLG allowed
• 25.5% whiff rate
• -9 run value

Brown’s four-seamer since May 22:

• .193 BA / .307 SLG allowed
• 30.7% whiff rate
• +12 run value

Meanwhile, Brown’s sinker has been instrumental in helping him substantially cut down on the amount of hard contact he allows. Of the 93 batted balls he has allowed on sinkers this season, only 11 (11.8%) have been hit hard.

Overall, Brown’s hard-hit rate has dropped 14.5 percentage points since last year, the largest decrease for any qualifying pitcher. His 29.9% hard-hit rate ranks in the 98th percentile, one year after he placed in the 13th percentile with a 44.4% hard-hit rate.

Yusei Kikuchi has been a huge addition

With their rotation depth thinned out by injuries, adding a starter was a priority for the Astros prior to the Trade Deadline. They paid a high price to acquire Kikuchi, a rental starter, from the Blue Jays.

Houston sent its No. 9 (pitcher Jake Bloss) and No. 13 prospects (infielder Will Wagner) along with outfielder Joey Loperfido to Toronto for Kikuchi, who had a 4.75 ERA at the time of the deal.

The move has worked out well for the Astros, with the 33-year-old lefty recording a 3.07 ERA with a 3.23 FIP and a 53-to-10 K/BB ratio over 41 innings spanning seven starts.

Much like Valdez and Brown, a change in pitch mix has had a lot to do with Kikuchi’s turnaround.

Prior to the trade, Kikuchi regularly featured both a slider and a curveball. But since joining the Astros, he has increased his slider usage while rarely throwing his slower curve, the less effective of the two breaking balls.

As Eno Sarris recently noted in his breakdown of Kikuchi for The Athletic (subscription required), the southpaw also has changed up his slider location when pitching to right-handed batters, more frequently targeting the low outside corner of the zone and going down and in less.

Additionally, Kikuchi has been elevating his four-seam fastball more against righties than he did with Toronto, with a specific focus on keeping his heater up and away.

These tweaks have made a big difference for Kikuchi against righties. With Toronto, right-handed batters hit .280 with a .441 SLG against Kikuchi. But with Houston, he has limited righties to a .196 average and .357 SLG.

The lefty's ascendance has made it less of a necessity for the Astros to get Verlander back on track in time for the postseason. If Verlander truly isn't a viable option, Houston could give the ball to Ronel Blanco, who threw a no-hitter and ranks third in the AL in ERA (2.99). Spencer Arrighetti, who had a 1.95 ERA and 38.2% strikeout rate in August, is another possibility.

Point is, the Astros have enough arms to make another deep postseason run, no matter what happens with Verlander over the next few weeks.