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.