When the New York Yankees first came to Fenway Park in early July, they looked unstoppable.

All throughout the first half the Yankees ran roughshod over everyone they faced. They could pitch, they could hit, their defense was outstanding and their bullpen was lights out. In short, the Yankees had no weaknesses, and after taking the first two of four from the Red Sox they stood a season-high 38 games over .500, boasting a 61-23 record with a 15.5-game AL East lead as early as July 8.

At that point the Yankees could have gone .500 the rest of the way and still finished with 100 wins. Even if the club couldn’t quite maintain its torrid first half pace, the Yankees still looked set to finish among the winningest clubs in MLB history.

Now it’s not even a sure thing the Yankees will win the AL East.

Since that Friday night and entering Tuesday’s return to Boston the Yankees have gone 24-33 and seen their mammoth division lead dwindle at an alarming rate. The Yankees had a particularly abysmal August where they went 3-14 over a three-week stretch, and last weekend their lead over the second-place Rays dipped to just 3.5 games before they bounced back and took two of three from Tampa in a crucial series.

How did this happen? Simply put, early on everything that could have gone right, did. But lately? That luck has almost completely flipped.

Start with the injuries. Right now the Yankees have 15 players on the injured list, including everyday regulars Anthony Rizzo, DJ LeMahieu, Matt Carpenter and big trade deadline acquisition Andrew Benintendi. Slugger Giancarlo Stanton was also out for most of August, and with so many holes to plug the Yankees have been forced to get by with a shell of their usually fearsome offense. Tuesday’s lineup, for instance, featured third baseman Josh Donaldson (.224) batting cleanup, rookie Oswaldo Cabrera (.205) batting fifth and a collection of bench pieces and glove-first starters comprising the rest.

The Yankees are also without nine pitchers, including starting pitcher Luis Severino and key bullpen arms like Michael King and Aroldis Chapman. Many of those who remain have also come down to Earth after great starts. Among that group, starter Nestor Cortes Jr. went from a surprise Cy Young contender to just pretty good, and top reliever Clay Holmes lost the closer job after a Mariano Rivera-like start. The decision to trade starter Jordan Montgomery to St. Louis hasn’t aged well either, especially after he went 5-0 with a 1.45 ERA through his first seven starts with the Cardinals.

If not for Aaron Judge’s historic production, you have to wonder how bad things could have gotten.

Even amid all of their struggles, the Yankees are still in full control of their destiny. With a 5.5-game lead entering Tuesday, New York still has some breathing room to work with, and after this week’s series in Boston they’ll play 10 of their last 19 games against sub-.500 clubs, including four straight against the Texas Rangers to end the season.

If the Yankees can get healthy, finish strong and make a deep run in the postseason, nobody will remember or care about the club’s second half struggles. But what once seemed like a formality is now far from assured, and if the Yankees hope to win the AL East and eventually their 28th World Series title, they’re going to have to earn it.

Email: mcerullo@northofboston.com. Twitter: @MacCerullo.