We’ve seen this before.

In 2008, Clay Buchholz was a rookie with all the promise in the world who became shocked by his own failures. After a respectable start (3.71 ERA through his first 10 outings with a 2-2 record), his season got derailed and could not get back on track.

Over the next 10 games, the right-hander was able to strike out batters (39 in 42 innings) but fell into a pattern of being undone by the twin vices of walks (27) and home runs (8). He went 0-7 with a 9.21 ERA during those 42 innings, and his struggles became so severe that the Red Sox tried a couple strategies -- a skipped start here, an inning out of the bullpen there -- before they were left with a pitcher who simply no longer looked ready to compete at the big league level.

Buchholz was sent down to Double-A Portland, a demotion that required him to swallow his pride, reconsider how he attacked hitters and work his way back. He did so.

The right-hander made it back to Boston after the All-Star break in 2009 and emerged as a top-of-the-rotation starter for much of the next two years in the majors, until his back injury left him unable to pitch in the middle of 2011.

But he’s no longer that. In fact, statistically he is now the worst starter in the major leagues, and his stuff bears little resemblance to the pitcher who ranked second in the American League in ERA in 2010.

Buchholz suffered his latest awful performance in Sunday’s 9-6, 17-inning loss to the Orioles, on a day when his inability to provide innings delivered a wrecking ball to an overtaxed bullpen. Buchholz lasted just 3 2/3 innings (his shortest outing of the year) while permitting five runs on seven hits and four walks.

He gave up three homers, bringing his total allowed for the year up to 10. In just 32 2/3 innings this year, he has been taken deep as many times as he was in 82 2/3 innings in 2011 and, more stunningly, one more time than he was in all of 2012.

“He left a lot of pitches in a real hittable zone and gave up a lot of hard-hit balls,” manager Bobby Valentine said. “Clay’s performance was not what he wanted it to be, for sure, and not what I wanted it to be.”

His ERA (9.09) ranks last in the majors among starters who qualify for the ERA title. His WHIP (2.02) is likewise the worst in the majors. He’s walking nearly as many batters (19) as he’s striking out (20). Opponents have a staggering .428 OBP and 1.041 OPS against him (both marks, again, last in the majors).

In short, he’s been awful.

The significance for the Red Sox is immense. The Red Sox had confidence that they could have one of the better starting staffs in the American League -- certainly an above-average one -- if Buchholz could rejoin Josh Beckett and Jon Lester as starters with All-Star-caliber abilities.

Had Buchholz remained healthy in 2011, virtually everyone around the Red Sox believes the team would have made the playoffs. The September collapse reflected in no small part his absence, and so his restoration to the rotation was expected to buoy the club.

But instead of providing helium, Buchholz has been dead weight. He has played a central role in the fact that the Sox rotation features a 5.72 ERA that ranks second to last in the major leagues. His inability to provide innings on Sunday was particularly glaring, both because the Red Sox bullpen already had logged 13 1/3 innings on Friday and Saturday and because it ended up having to endure another 13 1/3 innings on Sunday.

Buchholz insists that he’s healthy, that neither the back injury that ended his 2011 season nor the blister that cropped up entering this start was a relevant consideration. He also dismissed the idea that he is engaged in another psychological drama along the lines of the one that played out during his struggles of 2008.

“I don't feel mentally messed up at all,” he said.

Yet if he is not struggling with his health or psyche, then his struggles can seem almost more vexing.

“It's a pretty frustrating deal right now,” Buchholz acknowledged after the game. “I feel good. If I knew the reason I was giving up hits and runs, I'd probably fix it. I have to figure it out.”

There have been few stretches to provide a glimpse that Buchholz’s struggles will go away soon. He has allowed at least five earned runs in each of his six starts this year. The last time a Sox starter endured such a sustained stretch of struggle? That would be 1925, when Red Ruffing had eight straight starts of that scale.

Back when he was singularly dominant in 2010, Buchholz thrived while featuring 95 mph fastballs of both the two- and four-seam variety, both of which got tons of grounders (as did a cutter he developed that year). His primary off-speed offering was a devastating changeup that he used roughly one out of every five pitches; when batters swung, they came up empty on roughly one of every four cuts. His curveball was an occasional show-me pitch.

This year? According to the spectacular brooksbaseball.net, Buchholz has averaged 93 mph on his four-seamer and 92 mph on his two-seamer. He’s almost abandoned his changeup, throwing it just 8 percent of the time, and his swing-and-miss rate has been cut roughly in half (from 24 to 12 percent) on the pitch.

As such, Buchholz has turned on many occasions from his changeup to his curveball as his out pitch, and while he can spin some good ones, the hanger that he left over the plate to J.J. Hardy (which bounced off a sign atop the Monster seats and bounced onto Lansdowne Street) offered a reminder of the perils and limitations of the pitch.

In short: Buchholz has gone from a pitcher with two kinds of dominating fastballs, a solid cutter and a changeup that ranked as one of the best pitches in baseball to a hurler with two pedestrian fastballs and no confidence in his changeup. He has a curve that is, at times, above average but that remains inconsistent.

The Clay Buchholz of 2012 far more closely resembles the one whom the Sox demoted in 2008 than the one who dominated the American League in 2010, raising the question of whether the Sox must now consider the same alternatives to keeping Buchholz in the rotation that they explored in that rookie season.

For now, manager Bobby Valentine said, the Sox are not contemplating the removal of Buchholz from the rotation.

“I have no plans,” Valentine said, “to change him at this time.”

And what choice do they have right now? Alternatives are in short supply.

With Aaron Cook on the disabled list, the Red Sox do not appear to have immediate rotation alternatives to riding out Buchholz. Daisuke Matsuzaka, who is starting in Triple-A Pawtucket on Monday, likely will need at least one additional start beyond that one while working his way back from Tommy John surgery before he is big league ready.

Beyond Matsuzaka, the Sox have Justin Germano and Ross Ohlendorf as their Triple-A insurance options, pitchers who are competent but who haven’t shown the combination of performance and stuff to suggest an obvious and dramatic upgrade.

Still, it is worth noting that the Red Sox do have one option left on Buchholz, giving them the ability to send him to the minors. Because the right-hander is more than three years removed from his big league debut, he would have to pass through optional waivers in order to be sent to the minors. But he almost certainly would not be claimed, since that form of waivers is treated as a mere procedural technicality by major league clubs.

Yet while Valentine’s suggestion indicated that the Sox won’t go the demotion route in the immediate term, the team can ride out Buchholz’s struggles for only so long. The Red Sox know it and Buchholz knows it, even though he did admit after Sunday’s outing, for the first time, that it is taking him time to find his way back due to the time lost in 2011.

“I sometimes forget it, too, but everyone knows that until my first start this year, I didn’t pitch in an actual big league baseball game for seven months. Sometimes I’ve got to look back and take that in perspective, too,” Buchholz said. “It’s tough being off and then coming back right into the thick of things, especially with this organization, because you’re expected to win. Especially when your team is on a little slide or whatever, everyone wants to be that guy to take them out of that.”

That said, there will be little pity for Buchholz, either from others or himself. He understands that the results must take a dramatic turn immediately if he is to prove that 2012 is not 2008 redux.

He insists that he is putting in the work to achieve a turnaround, whether studying advanced scouting reports of his opponents or looking at video of his mechanics in 2010 to look for evidence of changes in his delivery now. But on Sunday, those efforts once again went for naught. Buchholz is willing to keep pursuing solutions, yet he remains baffled that none has arrived yet.

“I’m getting paid to do this job, so I’ve got to find a way to get through it,” he said. “I don’t know if I’m not thinking enough. I know I’m preparing enough. I prepared for this start today more than I have any other start all year as far as scouting, looking at video, reading up and stuff.

“It’s just, I think the years that I’ve thrown good, when I’ve made a mistake they’ve either fouled it off or swung and missed it. It seems like every mistake I’ve made this year has been a home run. It’s different this year,” he continued. “But it will work out. It has to.”