As the calendar flipped to August over the weekend, the Phillies acknowledged the obvious.

Behind Zack Wheeler and Aaron Nola, their starting pitching wasn’t nearly good enough.

So, a day after acquiring Kyle Gibson from the Rangers, Phillies manager Joe Girardi announced two additional changes.

No more Matt Moore. No more Vince Velasquez. The two pitchers combined for an unsightly 9.37 ERA in 10 starts last month, allowing 42 earned runs over just 40 1/3 innings.

Joining Gibson in the Phillies’ rotation makeover would be Chase Anderson and Ranger Suárez.

Gibson made a strong first impression yesterday, limiting the Pirates to just two runs over 6 2/3 innings. The Phillies received the type of competitive start they will be banking on more of down the stretch.

But behind Gibson, things remain unsettled.

The team will set the bar low by simply hoping Anderson gives them a chance when he takes the ball, something Moore and Velasquez too often failed to do. Still, Anderson meeting even the most modest of expectations is no sure thing given he pitched to a 6.96 ERA over seven starts earlier this season. A bullpen demotion and an eventual stay on the COVID-related IL followed.

Anderson wasn’t particularly impressive during an extended rehab stint with Lehigh Valley, posting a 5.71 ERA over five appearances, but he has been serviceable in two low-leverage relief appearances since rejoining the Phillies.

Again, it’s a low bar.

But the team will hope Suárez provides a more substantial impact. The 25-year-old emerged as Girardi’s best bullpen bet this season, ultimately providing some stability to the closer role in a limited sample despite a lack of traditional late-inning stuff.

In 27 relief appearances this season, Suárez had a pristine 1.12 ERA and 0.87 WHIP,  making the decision to move him into the rotation –and thus weakening an already thin bullpen — a significant gamble.

The Phillies could have opted to add another starting pitcher at the trade deadline, allowing Girardi to pair Suárez with the newly-acquired Ian Kennedy.

That duo would have provided two quality late-inning options, something Girardi hasn’t had since coming to Philadelphia. Relatedly, perhaps Suárez would have been on the mound in a tie game during the ninth inning Saturday night instead of José Alvarado, who yielded a leadoff double and again struggled with his command in an eventual walk-off loss.

A second rotation addition would have afforded Suárez an opportunity to flourish in a role with which he had clearly grown comfortable. But that second addition didn’t happen, so now the Phillies will hope he handles an in-season role change better than the recently-traded Spencer Howard, who seemed to acknowledge Sunday the organization’s ever-changing plans played at least a part in his struggles.

Despite not throwing more than 47 pitches in a game this season, the team believes Suárez can be stretched out on the fly in the middle of a National League East race that remains wide open. Or, in the absence of true belief, it is desperate enough to find out.

How Suárez approaches the transition will be worth watching. Much more goes into such a move than changes to routine and preparation. It’s not just about going from throwing 15-25 pitches a few times a week to throwing 80+ pitches every five days or dealing with a different game flow.

Pitch arsenals and plans of attack are also typically tweaked, and this is where I’m most curious to see this how experiment plays out.

At the expense of generalizing and perhaps over-simplifying things, most starting pitchers rely a diverse pitch selection. It’s extremely rare for an effective starter to rely on a two-pitch mix as he works through opposing orders throughout the course of a season.

That’s not necessarily the case for relievers, many of whom often thrive for short spurts featuring just a two-pitch mix.

Suárez, who is a starter-turned-reliever-turned-starter, has four pitches.

Prior to this season, he featured a fairly balanced four-pitch mix that included a sinker, changeup, four-seam fastball, and slider. In both 2019 and 2020 (a 52 2/3 innings sample), he featured his slider in 20.2% of his pitches. During that time, he also featured his four-seam fastball in roughly 25% of his pitches.

This season, however, Suárez has cut down on his four-seam usage (19.3%) while almost entirely eliminating his slider (6%). Instead, he’s thrived with a heavy changeup and sinker mix that accounts for nearly 75% of his pitches.

While he hasn’t become a true two-pitch guy, he began trending that way this season, and he had outstanding success doing so. Opponents are hitting just .129 against his sinker and .146 against his changeup this season.

His reliance on those two pitches has limited the damage on his four-seam fastball and slider. Opponents are hitting .240 with a modest .280 slugging percentage against the fastball and haven’t produced a hit yet against his slider, simply because he rarely throws it.

As a point of comparison, let’s rewind back to the 2019 season (he appeared in just four games last season) when opponents hit .263 and .283 against his sinker and changeup, respectively, while hitting .262 against his fastball and .314 against his slider. In the case of the slider, opponents slugged a wild .629 against it.

Watching Suárez work as a starter, which begins tonight in Washington, will be interesting for several reasons, many of which extend beyond the simple matter of whether or not he can keep runs off the board.

Will a move back to the rotation mark a higher usage of the slider and/or fastball, or will he continue to rely on his current pitch mix and simply take his chances? Will he be able to maintain a consistent feel for his pitches as he extends deeper into games? Will his command and velocity hold up?

The Phillies are making a significant –and perhaps desperate — “yes” bet on the above questions. The fate of their season may very well depend on being right.