Buchholz has not pitched in six weeks and seemed close to returning before the Red Sox decided to send him to another specialist. The results of that visit were not encouraging and now Buchholz will be shut down.
It's a big blow for the Red Sox, who were already having trouble finding five live arms. Buchholz had a 3.48 ERA in 14 starts this season and seemed to be penciled in as the No. 3 starter in a playoff series.
However, with Buchholz out the Red Sox must explore alternatives. We know Jon Lester and Josh Beckett will be at the front of the rotation, but who's behind them?
Here's a look at all the potential candidates to fill the void left by Buchholz.
The most obvious candidate to fill Buchholz's spot is Erik Bedard.
The Red Sox acquired the lefty from the Seattle Mariners at the trade deadline for a collection of prospects, and plan to insert him into the rotation immediately.
Bedard, 32, has a 3.45 ERA in 16 starts this season and an impressive 8.6 SO/9. However, Bedard has battled shoulder injuries for years and just recently returned from a stint on the disabled list.
Bedard got roughed up in his first start back, but the Red Sox apparently liked enough of what they saw to make a move.
When healthy, Bedard is one of the better left-handers in baseball and certainly good enough to start the third game in a playoff series. The big question is if he will stay healthy?
Bedard hasn't thrown more than 100 innings since 2007, and he's set to break that barrier in about two weeks.
Miller started off his Red Sox career on a high note, but as teams started to get used to him and the level of competition went up, Miller, naturally, went down.
On the season he has a 5.36 ERA and 1.88 WHIP in eight starts. He's walked just as many batters (25) as he's struck out in just over 40 innings.
The 26-year-old lefty definitely has talent, but a pennant race is no place for a young pitcher to get his feet wet. And especially not in Boston.
Unfortunately, the Red Sox don't have too many other options so Miller stays in the rotation until he gives manager Terry Francona a reason to take him out.
The Red Sox love what Aceves can do, but they'd much rather he do it in the bullpen.
The 28-year-old righty has a 3.19 ERA in 31 games, but only four of those were actually starts. In those four starts Aceves pitched a grand total of 21 innings and gave up 12 earned runs, so he hasn't exactly been lights out.
Aceves seems more comfortable in a bullpen role, and that's where Francona wants to keep him. Inserting him into the rotation is a last resort.
Kevin Millwood has had a long and productive major league career, but as of right now he's spending his time pitching for AAA Pawtucket.
The 36-year-old righty is 5-1 with a 4.12 ERA in 12 starts for the Paw Sox. His strikeout totals (63 in 67.2 innings pitched) are encouraging, but hardly evidence that he'll be able to consistently get major league hitters out.
The last time Millwood was in the majors he lost a league-high 16 games and finished with an ERA north of five. There's a reason he's in the minors.
The Red Sox will likely have Millwood make a start for the big league club and, depending on how he does, decide if he deserves a more permanent spot in the rotation.
It's still hard to fathom any scenario in which Millwood makes Boston's playoff roster, regardless of his 41.1 postseason innings.
Doubront is the other name to keep an eye on in the Red Sox minor league system.
The 23-year-old lefty made three starts for the Red Sox in 2010 and pitched reasonably well. He was the logical choice to be the first starter called up to Boston if the Red Sox needed a short-term replacement, but injuries prevented Doubront from starting the season on time and he's been back and forth on the disabled list.
In 10 starts at AAA Pawtucket, Doubront has a 3.53 ERA and batters are hitting .242 against him. But just when it looked he was starting to get going Doubront landed on the DL again, this time with a hamstring strain.
He'll be back soon, but the Red Sox might be better off not rushing him at the major league level. He projects as a back-of-the-rotation starter.
Wakefield has saved the Red Sox rotation more than once in his career. However, it may be a bit much to ask a 44-year-old knuckle-baller to be a championship team's No. 3 starter.
Because right now that's what Wakefield is.
With John Lackey still determined to win the award for most overpaid player in baseball, Wakefield finds himself as the third most reliable starter in the rotation.
That said, Wakefield has a 5.03 in 23 games, 14 of which were starts. In those 14 starts Wakefield has pitched seven or more innings just five times, although he's made it past the fifth inning all but once.
Wakefield can give the Red Sox innings, but he can't match up against a Phil Hughes or a C.J. Lewis in a playoff series. So who do the Red Sox turn to?
The Red Sox will pray to the baseball gods that Erik Bedard stays healthy enough to make it through an entire season, because there's nobody else on the roster who can match his talent and ability.
In the short-term, Wakefield and Lackey will round out the rest of the rotation, while Andrew Miller gets sent back down to Pawtucket to work on his form some more.
We will see Kevin Millwood in a Red Sox uniform at some point, although it won't be in a positive light. If one of Lester, Beckett, Bedard, Wakefield or Lackey can't make a start, Millwood's likely the first one to be called up.
However, a rotation of Lester-Beckett-Bedard-Wakefield-Lackey doesn't exactly scream October, unless Bedard and Lackey both start pitching like they're still in their primes.
The Red Sox could explore the waiver market, but none of the names (Wandy Rodriguez, Livan Hernandez) inspire much confidence. This next month should help determine if the Red Sox are serious contenders or just a first round exit waiting to happen.