Daisuke Matsuzaka is now more than halfway through the six-year deal that he signed with the Red Sox prior to the 2007 season. And yet, somehow, he remains the source of absolute befuddlement.

The pitcher remains capable of dominating an opposing lineup, a notion evident as recently as Saturday, when he carried a no-hitter into the eighth inning against the Phillies. But he is also capable of running completely off the tracks, as he did in the fifth inning of his 4-3 loss to the Royals on Thursday. (Recap.)

Matsuzaka allowed just two hits, meaning that, in his last two starts, opponents are hitting just .077 against him (3-for-39). On the season, hitters have just a .218 mark against him.

Yet even with the Royals showing little ability to barrel his pitches, Matsuzaka walked a startling eight batters (matching a career high), including five in a three-run fifth (most by a Sox pitcher since May 11, 2002, when Darren Oliver matched that total). He added in a hit batter and wild pitch.

“Obviously, Dice kind of lost it for a little bit there,” noted utility man Bill Hall, who played center and homered on Thursday.

Of course, every pitcher is entitled to such a game on occasion. Faltering command — along the lines of what Matsuzaka experienced in the fifth, when his fastball was missing the plate by several inches — happens on occasion.

But for Matsuzaka it is commonplace, even on nights when he is unhittable. He now has two games in his career in which he’s allowed two hits and eight walks. No other active major leaguer can make such a claim.

Perhaps it is the language barrier or cultural norms that make the explanations for his struggles seem inscrutable. Even so, it is the case that his inconsistencies are explained by a dizzying (and ever-changing) number of theories.

Dating back to 2007, there have been issues related to the American baseball, the strike zone and the different batting philosophies of Major League Baseball hitters from their Japanese counterparts. There have been disputes over conditioning methods, and struggles adjusting to American hotel beds. On occasion, there have been suggestions that the signal calling of his own catchers are responsible for poor performances.

There have been shoulder problems, leg problems, back problems and neck problems. On Thursday, Matsuzaka (3-2, 5.77) suggested that “lower body soreness” contributed to a night in which the pitcher matched a career high by allowing eight walks, including five in a disastrous fifth inning.

“I think, mechanically, my lower body wasn’t cooperating with me today, and I think I had to rely too much on my upper body,” said Matsuzaka (through translator Masa Hoshino), who did allow that the soreness was not the sole cause of his poor outing. “It’s been a long time since my body didn’t cooperate like this. The velocity was there, but there was no movement or bite to my pitches, not to mention any command.”

The description of that injury was somewhat puzzling, particularly since no one else on the team recognized it as a concern. Catcher Jason Varitek noted that the pitcher was “powerful,” and his 92-94 mph fastball seemed, at times, did exactly what both the pitcher and catcher expected. Yet by the end of the night, Varitek was left to engage in a lengthy postgame discussion with Matsuzaka and interpreter Hoshino in the Sox clubhouse to figure out the cause of a game where it made little sense for him to struggle.

“He’d have it for a click. He was still powerful. And then, obviously, it would run awry on him,” Varitek said. “He just couldn’t find a way. Usually he can find one or two pitches to slow him down, but we just couldn’t slow him down. He was pretty amped.

“Obviously, he was struggling with his command and his release point. At different times, he was able to throw through me. At other times, his arm would drag or his arm would be in front. I don’t know what the answer is, but I know he’ll do the work to try to figure it out.”

There was a need to sift through the aftermath of this game. The notoriously impatient Royals, after all, should have been the ideal opponent for the Red Sox starter.

Consider:

-- Entering Thursday, the Royals ranked last in the American League in walks (129).

-- They had taken free passes in a league-low 7.2 percent of plate appearances.

-- The Royals were the only team in the majors not to have walked more than six times in a game this year. In fact, all of the other 29 clubs had at least two games of seven or more walks prior to Thursday.

Yet the Royals looked like their lineup was comprised of nine clones of Kevin Youkilis on Thursday, thanks to a starter who often missed his spots by large margins.

Matsuzaka’s walkapalooza resulted from a sudden and total loss of his fastball command. Through four scoreless innings, the pitcher had thrown 27 of 43 fastballs (63 percent) for strikes. Then … poof. He lost the ability to locate the pitch.

In the fateful fifth, Matsuzaka threw fastballs on 34 of his 42 pitches. Of those, just 13 (38 percent) went for strikes.

The Sox have had to resign themselves to the idea that, even on days when the opposing lineup can do little with his stuff, the pitcher will still seem reluctant to throw strikes. Since he broke into the majors, Matsuzaka has had seven starts in which he has allowed two or fewer hits but four or more walks, tied for the most in the majors (with San Diego’s Chris Young) in that span. Opponents have hit just .243 against him (third-lowest in the AL among pitchers with at least 400 innings), yet his 4.35 walks per nine innings are the most in the AL during that time.

On the one hand, the pattern is frustrating for the Sox. It means that the bullpen stands a good chance of being taxed when Matsuzaka is on the mound, and it suggests that, on any given day, it will be unclear whether Matsuzaka will be able to position his club to win.

On the other hand, even when he is missing the strike zone, he has an ability to limit the damage. The fact that he allowed just three runs on Thursday amidst his terrible command lapse is a reminder that he is capable of a bizarre bend-don’t-break style.

“That’s kind of part of the pitcher that he is,” pitching coach John Farrell said. “While the overall strike percentage might not have been the highest, he somewhat was effectively wild to his advantage.”

In the fourth, Matsuzaka was able to narrowly escape disaster. After loading the bases with no outs, he got three straight pop-ups to keep Kansas City off the board. But, in the fifth, he could not sustain his escape act.

He walked Chris Getz, owner of a .263 OBP, on four pitches to start the inning, one of three leadoff walks he conceded on the night. After getting his only strikeout of the night, he walked Mike Aviles — just the second time that the shortstop has walked in 87 plate appearances this year.

He then gave up a run-scoring single, walked cleanup hitter Billy Butler to load the bases, then walked Jose Guillen to force in a run. After a forceout at the plate, Matsuzaka bounced a slider to push home another run. He concluded his night by walking Mitch Maier to re-load the bases. After 112 pitches (and just 60 strikes), Matsuzaka’s night was done.

It was a game that highlighted the challenge of managing such a pitcher. Farrell noted that Matsuzaka "seemingly lacked command from start to finish." With most pitchers, it would be easy to determine that the pitcher was simply having an off night, and to make the call to the bullpen early in the fifth. With Matsuzaka, there is guesswork as to whether a game is getting out of hand or if he is about to conjure a way out of a crisis.

“The inning before, bases loaded, nobody out, he makes pitches [and gets out of it], But you keep doing that, at some point, you're going to get nicked up,” Sox manager Terry Francona said. “We’re sitting on the edge of our seat with the seat belt on. He wiggles out of it one inning, he came pretty darn close the next inning.

“It’s a hard way to pitch successfully. He has a unique ability to get out of some of those situations, but it’s a difficult way to pitch.”

Yet that difficult pattern remains one that the Sox are unlikely to see Matsuzaka shed anytime soon. The 29-year-old is at a point in his career where a radical change is unlikely.

And so, the team is left to buckle up every fifth day, and hope that Matsuzaka leads the Sox to safety more often than he crashes.