There was a fascinating symmetry to the setting.

After all, the beginning of the end of Daisuke Matsuzaka’s days as a meaningful contributor in the Red Sox rotation had come in the same ballpark, with a similarly dramatic bellyflop. On April 14, 2009, the right-hander got blown out in Oakland, allowing five runs on five hits and two walks in one inning, a performance in which his non-existent fastball velocity led the Sox to the immediate conclusion that he needed to be placed on the disabled list.

Prior to that point, Matsuzaka had been an important contributor in the Red Sox rotation. In two years and a start, he was 33-16 with a 3.77 ERA, coming off of two years in which he finished fourth in the Rookie of the Year voting and then fourth in Cy Young voting. Yes, he could be maddening, but the bottom line was that he was ultimately effective and a key component of the Sox rotation.

But that ceased to be the case that day in Oakland. In the subsequent three-plus years, he has spent far more time on the DL than off of it, a pitcher whose health has been characterized by fragility and who has remained engaged in a seemingly constant search for a comfortable routine that has borne little evident fruit.

And on Monday night, back in Oakland, there (more or less) was that line again: One-plus innings, five runs, four hits, two walks, no strikeouts in a 6-1 Red Sox loss to the A’s that became an inevitability when Matsuzaka walked off the mound having thrown just 28 pitches, most of them ineffective on a night when his fastball velocity dropped into the high-80s and when he did not get a single swing and miss. It was the third time that Matsuzaka has made a start in which he’s recorded no more than three outs, making him the lone Red Sox pitcher over the last 20 years to have three starts of such brevity.

Between those two one-inning stints, Matsuzaka has appeared in just 48 games over roughly three and a half seasons. He is 16-17 with a 5.14 ERA, the sustainable runs of success having been few.

Still, he was amidst a six-year contract, and so the Red Sox had little choice but to write him into the rotation and hope that his health would hold up and permit him to perform at a high -- or at least adequate -- level. And every now and again, he would offer a tease, overpowering an opposing lineup in a fashion that reminded everyone why the Sox were willing to pay $103 million to acquire him to so much fanfare all those years ago.

But as often as not, he’s been a liability in the rotation, someone whose performance was barely fit for the role of a fifth starter on a winning team and whose availability was in question. And Monday night underscored both aspects of the uncertainty that surrounded him, a terrible outing in which Matsuzaka could not pitch through the discomfort in the right side of his neck (the trapezius muscle, to be more precise).

The 31-year-old deserves credit for his rapid recovery from Tommy John surgery. In some ways, it was startling that he was able to start a game just 12 months after he underwent the procedure, and team officials raved about the work he invested into his rehab process.

And there was, again, promise that he could be an effective or at least serviceable contributor. Though winless (0-2) in his first four starts back from the DL, he’d been good enough to keep his team in each of those contests, pitching at least five innings in each of them and allowing no more than four runs. Perhaps most intriguingly, he struck out 20 and walked eight, a suggestion that he possessed swing-and-miss stuff but that, post-Tommy John surgery, he was commanding it better than before.

And then came Monday.

“[Matsuzaka] obviously didn’t have his good stuff tonight and he went out with a crick in his neck, and we were hoping he was going to work through it. As it turned out, he didn’t work through it,” Sox manager Bobby Valentine told reporters. “A couple of days ago, it was stiff but it seemed like he worked through it. He said he was going to be all right to pitch. We asked him pretty consistently.”

Matsuzaka told reporters after the game that he was dealing with the same problem that affected his rehab progression both in spring training and again at the end of May, when he required a cortisone shot. The right-hander had been unable to throw a bullpen session between starts, and told reporters (through a translator) that his “body wasn’t in the condition it probably should have been.” He suggested that he would move immediately to have the problem treated once again.

Yet the forthcoming downtime, which will render him unavailable for at least one start in the final weekend of the first half and possibly more depending on whether the Sox place him on the disabled list, may serve as the effective endpoint of the pitcher’s time as a regular member of the Red Sox rotation.

His contract has dwindled to its last half-season. The idea of Matsuzaka’s upside and his long-term place in Boston no longer governs decision-making regarding his place in the rotation.

Need (whether created by the health or effectiveness of other starters) could still result in more starts for Matsuzaka. Obligation will not.

There is a game of musical chairs in play with the Red Sox rotation, at a time when Jon Lester and Josh Beckett are the staples, Clay Buchholz will join them whenever he is healthy, Felix Doubront has asserted himself (his recent struggles notwithstanding), Franklin Morales has dazzled in his rotation trial and Aaron Cook likewise was masterful in his most recent start.

Matsuzaka, until Monday’s struggle, had been serviceable. But just as was the case three years ago in Oakland, he walked off the mound with a question mark hanging over his head, a prevailing uncertainty about what he might be able to provide going forward. In the past, the Sox have always felt compelled to let the question play itself out with some semblance of an answer. But now, the compulsion may yield to a more pragmatic approach.

There remains a chance that Matsuzaka reasserts himself after getting his neck treated. Perhaps Doubront's innings will need to be managed, or Morales will prove a flash in the pan, or Buchholz will remain sidelined for longer than expected. And perhaps, after receiving treatment, Matsuzaka will be able to go on the same sort of effective run that characterized his performance in Triple-A and the majors in the month of June.

But perhaps not. There is an increasingly real chance that Matsuzaka’s days as a relied-upon rotation member in Boston might be done. A pitcher who was acquired to be an anchor is instead finishing his Red Sox career somewhat adrift, pushed by the currents of other members of the rotation rather than defining his own route.