THUNDERING HEARD

It was laughable to think the Lakers would face a must-win situation against Oklahoma City in April after beating the Thunder back in December, improving to 23-4 while the Thunder fell to 13-14.

But there was not much hilarity around the Lakers’ practice facility Monday going into a pivotal Game 5 against the Thunder at Staples Center.

A Lakers loss Tuesday means the unthinkable -- a possible elimination game Friday in Oklahoma City, against a franchise they had defeated 12 consecutive times before losing there last month by 16 points and last week by five and 21 points.

Their hopes of a championship repeat currently come down to a victory in Game 5, their best-of-seven series tied at two games each.

“Of course, it’s a must-win,” Andrew Bynum said Monday. “We have to go out there and win. There’s nothing else really to that.”

Kobe Bryant did not practice Monday to rest a right knee that was swollen enough to require almost round-the-clock attention in Oklahoma City, his day sometimes starting at 4:30 a.m. to begin massage therapy and other treatment.

Bryant’s knee is improving incrementally -- “I feel good right now,” he said Monday -- and the fracture in his right index finger has officially healed, though Bryant remains bothered by arthritis in a joint in the finger that will probably still warrant a protective device.

He knows his elevation has been lacking because of the knee. He has shot only 38.4% this series, the most inaccurate he has been in the playoffs since shooting 38.2% as a rookie in nine postseason games in 1997.

“It’s been tough,” he said. “Some nights have been tougher than others.”

The Lakers have the advantage of returning home after getting shelled in their last five quarters at Ford Center, but the pressure is squarely on them. Oklahoma City, after all, is ecstatic to be tied in this series after losing four of its last six regular-season games, prompting Bryant to acknowledge the Thunder is on a roll while “playing with house money.”

History is also placing some importance on Tuesday’s game. The Lakers are 17-0 in best-of-seven series when they win Game 5 at home.

“We can’t afford to lose this game,” Pau Gasol said. “It’s really a game where we want to establish ourselves, send a message to them that they might be playing well, they played really well at home, they got two games, but that’s all they’re going to get.”

Bryant didn’t sense the need to peddle any panic while talking to reporters Monday. He was annoyed by the context of some questions lobbed in his direction.

“Who said our backs are against the wall?” said Bryant, who has played in 179 playoff games. “It’s a 2-2 series. What the hell is going on around here?”

The Lakers had to scale down Monday’s practice because only nine players were on court. Bryant was out, DJ Mbenga was sidelined after undergoing more surgery on his left retina Sunday night, Josh Powell was at his wife’s side for the birth of their child, and Sasha Vujacic continued to miss time because of a sprained left ankle.

The Lakers will target one area in particular in Game 5: Oklahoma City has run them off the court this series, outscoring them in fastbreak points by a staggering 72-17 margin.

“We’ve got to get our [butt] back,” Bryant said. “It’s as simple as that. Their speed is remarkable. We’re obviously not as fast as they are, nowhere near.”

It starts with a more balanced offense and fewer outside shots. The Lakers averaged 26.5 three-point attempts per game in Oklahoma City, way too high for Coach Phil Jackson’s liking.

“A sound offense provides rebounding and defensive balance,” he said.

The Lakers have one thing going for them: Jackson will not be penalized for comments last week after saying NBA Commissioner David Stern is too “heavy-handed” in threatening to suspend coaches who criticize referees, according to a league source who requested anonymity.

Vujacic update

Vujacic said his sprained ankle was healing quickly and he hoped to return at some point in the next round if the Lakers get that far.

“My ankle is looking much better,” he said. “I’ve started walking slowly and, of course, I’ll do everything possible to be there.”

mike.bresnahan@latimes.com

twitter.com/Mike_Bresnahan

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(BEGIN TEXT OF INFOBOX)

How the Lakers can beat a faster, more athletic Thunder team

Better shot selection

The Lakers are averaging 24 three-point shots a game in the series and missing 71% of them; misses trigger long rebounds and Thunder fastbreaks. More makes = fewer Thunder breaks.

Finish near the hoop

The smaller Thunder has been packing the paint on defense, so 7-footers Pau Gasol and Andrew Bynum, 6-10 Lamar Odom and 6-7 Ron Artest have had trouble scoring down low.

Wake-up call

Artest, Odom and Jordan Farmar have been disappointments. Farmar, 23, is athletic, but you wouldn’t know it when he’s tried to defend Russell Westbrook and the other Thunder guards.

Slow the Thunder’s fastbreak

The Lakers can send some perimeter players back upcourt to defend after a shot goes up. The Lakers would lose some offensive rebounds, but it would help slow Westbrook & Co.