Kobe Bryant sat in his chair wearing a black robe, his feet in a bucket of ice, his answers to every question curt, yet straightforward and clear.

None of his answers were more succinct than when Bryant was asked to grade the Lakers' defense against the Boston Celtics during Sunday's 109-96 defeat at Staples Center.

"F," Bryant said.

Why?

"Well, we didn't execute well," Bryant said. "We blew too many assignments."

Enough to allow the Celtics to rip holes in the Lakers' up-and-down defense.

Enough to allow the Celtics to make a whopping 60.3% of their shots against the back-to-back NBA champion Lakers.

When Lamar Odom was told how well the Celtics shot, he replied with a question.

"How much?" Odom asked, raising his eyebrows.

Um, 60.3%, Odom was told again.

""Whew!" said Odom, shaking his head. "Sixty! They are too good to let them shot 60% from the field. You should expect to lose to the Boston Celtics if you let them shot 60%."

So what if Odom was off by 0.3.

He made his point.

And then there was Boston's three-point shooting against the Lakers.

The Celtics burned LA's exterior defense, making 52.9% (nine for 17) of their three-point shots.

Boston didn't shoot less than 50% from the field in any quarter.

The Celtics shot 68.8% from the field in the third quarter.

And they were just getting warmed up.

The Celtics blitzed the Lakers' defense in the fourth, making a scorching 70% (14 for 20) of their shots.

Ron Artest was the hero of Game 7 last June, keeping the Lakers in the hunt long enough for a fourth-quarter run that made them NBA champions for a 16th time.

He had 20 points and five steals that night against Boston, enough for Lakers Coach Phil Jackson to call him the Game 7 most valuable player because "he brought life to our team, he brought life to the crowd."

There was even a "Ron Ar-test, Ron Ar-test" chant, Lakers fans pumping him up while Kobe Bryant staggered to a six-for-24 shooting effort.

On Sunday, though, Artest was one of the main reasons for the Lakers' 109-96 loss to Boston.

His defense was shoddy against Paul Pierce and he made a numbing one of 10 shots, scoring only three points in almost 24 minutes. For the second consecutive game, he did not get off the bench in the fourth quarter.

Artest was signed to a five-year, $34-million contract in July 2009 specifically to shut down players such as Pierce.

Pierce had 32 points on 11-for-18 shooting, including three of five from three-point range Sunday.

"He played really good. He really gave it to me," Artest said. "He gave it to me last year in the regular season too."

In that Game 7 last June, Artest limited Pierce to 18 points on five-for-15 shooting.

But Artest was so askew Sunday that Jackson was asked whether the 12-year veteran got lost on the way to the game.

"No, he was on time. He got lost on the court," Jackson retorted.

Jackson noticed Artest's problems right away against Pierce — "What did he get, nine points right off the bat?" — and Artest never re-entered the game after leaving with 1:56 left in the third quarter.

Jackson chose his words carefully when asked about it, cognizant that Artest yelled at him during a practice this month because Jackson continually criticized him to reporters and in front of teammates.

"Ron took a couple shots that I thought were, like, perhaps not in the context of what we were trying to do," Jackson said. "I thought maybe we'd go another direction."

Artest said he was slowed after getting kneed in the right thigh on a first-quarter drive by Shaquille O'Neal.

"I wasn't able to continue to take [Pierce] and be aggressive," Artest said.

Artest, however, wasn't disappointed that Bryant gave the team an "F" grade for its defense against Boston. He took the optimistic approach.

"I got 'F's in elementary school," Artest said, "and I still went to college."

Not much dialogue

If the Lakers had played this way last June, there would have been no Game 7 victory, no champagne spray, no championship parade, no chance at a three-peat and, on a positive note, Ron Artest would have taken off his jersey on the night of June 17 instead of three fun-filled days later.

The season that won't straighten out continued to lurch and roll uneasily for the Lakers, who fell to the Boston Celtics, 109-96, Sunday at Staples Center, the latest indication that the defending champs are having trouble defending . . . and scoring . . . and sharing the ball . . . and just about everything else.

Kobe Bryant gave the Lakers an "F" for a defense that yielded a 59-point second half, a one-sided Celtics burst written in black ink on the whiteboard in the Lakers' locker room.

Paul Pierce scored 32 points and Ray Allen had 21 as the Celtics shot a remarkable 60.3% Sunday. Shaquille O'Neal (0 for 2) was the only Celtics player not to make at least half his shots.

The Lakers had a pathetic 10 assists, six fewer than Celtics guard Rajon Rondo, and their fans grumpily filed en masse for the exits during a timeout with 1:29 to play, the Celtics up 14.

The big picture continued to look bleak for the Lakers (33-15), now on a 3-4 skid while falling to the fifth-best record in the NBA. They are 1-4 against the teams ahead of them — Boston, Miami, San Antonio and Chicago.

"I think guys are just upset probably. They should be," Bryant said. "We're not playing very well against these top teams. So we need to elevate our level and we need to get better if we're to defend our throne."

Bryant had 41 points on 16-for-29 shooting, though he failed in his attempt to carry the Lakers to victory. At one point in the fourth quarter, he took shots on 10 consecutive possessions, and an 11th was ended by his offensive foul. He had 11 points on five-for-11 shooting in the quarter.

He was the only Lakers player to take a shot from when Pau Gasol missed a 10-footer with 7:20 to play until Gasol's missed tip with 1:44 to play.

Lakers Coach Phil Jackson pointed the finger not at Bryant, but his teammates.

"I didn't think anybody else wanted the ball," Jackson said. "We did run a couple other things to get people in position but I thought those times he had the best opportunities. A lot of times, it didn't look like we were running anything out there offensively.

"I think sometimes we fold into ourselves and let him have too much space out there at times."

The Celtics (36-11) came into the game as the NBA's top-shooting team, showing 49.9% accuracy, but they kicked it up a level Sunday. It was especially obvious against a Lakers team that couldn't seem to hit anything.

Artest made one of 10 shots and sat out the entire fourth quarter. Derek Fisher made one of six shots. Gasol had 12 points on five-for-13 shooting.

Bryant was irritated by the loss, but Jackson was more light-hearted, telling a reporter that the games didn't really count until the playoffs and also facetiously pointing out that the Lakers did one thing well.

"I think the only good defensive job we did out there was on Shaq," he said. O'Neal was scoreless in almost 13 minutes while battling foul trouble throughout the game.

Making matter worse for the Lakers: Boston was coming off a mystifying 88-71 loss in Phoenix in which Kevin Garnett and Celtics Coach Doc Rivers were ejected.

Garnett clearly outplayed Gasol on Sunday, finishing with 18 points on nine-for-12 shooting, 13 rebounds and five assists.

Pierce, however, was the bigger machine for the Celtics, ripping through Artest's defense from the start and making 11 of 18 shots.

"It's definitely an emotional game especially since losing Game 7 here," Pierce said. "It's a big game just knowing that we can come into this building and get a win."

Bryant was unstoppable in the first half, scoring 22 points on eight-for-11 shooting as the Lakers took a 54-50 lead. It would have been larger but Lamar Odom fouled Glen Davis on a halfcourt shot as time expired, allowing the Celtics forward to shoot three free throws, two of which he made.

The Lakers regressed in the third quarter, Pierce carving them up with 14 points and making all three of his three-point attempts. The Lakers entered the fourth down, 77-72, and moved within four with 5:20 to play before fading badly.

They wore throwback uniforms from the 1971-72 season, which ended with a championship victory against New York, but their effort Sunday wasn't reminiscent at all of their title-worthy performance last June against Boston.

"We have to get better," Bryant said. "There's no other option but that. You've just got to continue to work at it and work at it and work at it until you're at the championship level."

mike.bresnahan@latimes.com

twitter.com/Mike_Bresnahan

January 30, already?

(Yawn)

OK, how are we doing in the West?

Second place? Who's in first?

SAN ANTONIO?

We better get to work!

Everywhere else, the dog days run from the trade deadline, the week after the All-Star break, to April 1.

In Lakerdom, they start on Christmas and have lasted as long as the second round of the playoffs, as in the 2009 debacle, er, series against Houston.

In a handy lesson, the Lakers were on their way to winning a title in 2009, all appearances to the contrary.

All appearances to the contrary, they weren't dethroned Sunday when the Boston Celtics walked all over them in a 109-96 object lesson in who's whom in the pecking order.

We're talking humiliation … Celtics fans chanting "Beat L.A.!" … Celtics fan Matt Damon and friends yukking it up courtside between the Lakers' bench and superfan Norm Pattiz.

Happily for the Lakers, their world couldn't end Sunday.

It says so on the NBA schedule:

Tuesday — Houston.

Thursday — San Antonio.

Saturday — at New Orleans.

As Coach Phil Jackson said when asked about losing to all the good teams, smiling beatifically:

"Is it the playoffs yet?

"... We're playing regular-season games. We'll get there in time."