LAS VEGAS – Bernard Hopkins lost to the most destructive force in boxing Saturday night. He lost to the calendar – barely.

Joe Calzaghe will be credited with the win but it was the passage of time that really beat Hopkins down this night.

Twenty years in the ring and 54 nights spent trapped at close quarters with another man trying to assault you, chips pieces away from you that are left behind in the arena when you leave. That finally happened to Hopkins, as it does to all men who call boxing their business.

By the end of the night it was Hopkins, the master of the unseen dastardly deed who was looking to referee Joe Cortez for a point or a break, twice dropping to his knees claiming low blows. Cortez agreed but only barely, never taking a point from Calzaghe while giving Hopkins the breathers he was crying out for.

Midway through a fight Hopkins seemed to be in control of early, the 43-year-old RING magazine light heavyweight champion simply began to grind to a halt, throwing fewer and fewer punches and holding more than he ever had as the undefeated Calzaghe slapped and flurried his way to a split decision victory at the Thomas and Mack Center.

Judge Ted Gimza had Calzaghe winning 115-112, long-time Las Vegas staple Chuck Giampa saw it a lopsided 116-111 for Calzaghe while Adalaide Byrd scored it 114-113 for Hopkins, which seemed a bit of a career achievement award. The media at ringside seemed to favor Calzaghe but not completely, with some giving the nod to Hopkins by a close margin while others seemed surer that Calzaghe had won his second world title.

Among them was Calzaghe himself, who recovered from a first round knockdown to win his first fight outside of Europe by adjusting to the fight’s slow pace early and turning up his activity, if not exactly landing with great authority.

“I had to let the punches go as the fight went on,’’ Calzaghe (45-0) said. “He was very defensive. I knew this wouldn’t look pretty. He was so awkward. It wasn’t pretty but I know I won.’’

Hopkins wasn’t so sure of that. He stood staring out at the crowd of 14,213, most of whom were angry Brits, who were hollering at him all night, as he awaited a decision he felt would go his way. After the first two cards were announced, Hopkins began to nod his head as ring announcer Michael Buffer dragged out Giampa’s card. When he finally said it was for “the man from Newbridge’’ Hopkins had a surprised look on his face. It was the look of a man who didn’t realize he’d moved to Wales.

When it finally dawned on him that he had lost, he looked down at HBO’s broadcasting crew as if to say “Do you believe that?’’ The cable network’s “judge,’’ Harold Lederman, certainly did because he too had it for Calzaghe by a wide margin.

“I felt I controlled the pace of the fight,’’ Hopkins (48-5-1) said. “I felt it was an old school execution. He really wasn’t landing his shots.

“I really feel like I took this guy to school. I made him fight my fight not his. I felt like I made him look amateurish.’’

Frankly, at times he did. But Father Time often made Hopkins look like a man whose reflexes had begun to desert him, unwilling or unable to pull the trigger when the openings were there and then leaving him wondering why nothing had happened.

Yet the night did not start off that way. Whatever home field advantage Hopkins may have thought he had clearly disappeared before the first bell when Calzaghe entered the ring to thunderous applause while Hopkins, the self-proclaimed Yankee Doodle Dandy, was booed lustily by a crowd that was full of leather-lunged men carrying British passports.

Calzaghe seemed buoyed by the crowd’s affection, going to all four corners of the arena to blow a kiss and raise both hands in acknowledgement. Hopkins, meanwhile, stood briefly on the ring apron and made his familiar cross-armed “X’’ for Executioner sign as the boos rained down on him.

Hopkins seemed unaffected by this harsh reception, putting up the “X’’ sign a second time as he was introduced by ring announced Michael Buffer as the boos again cascaded down upon him until the first bell sounded.

In less than two minutes, Calzaghe was cascading toward the canvas, felled by a straight right hand behind a lazy Hopkins jab that seemed to distract Calzaghe for just long enough to allow the right to come in sight unseen and crack him square in the middle of his face.

Calzaghe tried to hold on to the back of Hopkins’ neck to prevent his fall but Hopkins half pushed him off as he was tipping forwards and down Calzaghe went, unhurt but seeming already unraveling.

The vaunted high volume of punches Calzaghe had promised was well off his normal 60-to-75 per round pace and that continued into the second round. Calzaghe seemed to follow Hopkins around, seldom throwing and not landing effectively when he did.

Calzaghe finally tried to begin pushing the pace more in round 3 and had some success but Hopkins would repeatedly tie him up when the super middleweight champion would flurry on the inside, thus blunting to some degree his offense simply by smothering it. While Hopkins did nothing special he was effectively doing as he’d promised, pushing Calzaghe out of his fight and turning it into the slower paced affair he needed it to be.

Yet Calzaghe was slowly beginning to score more often while Hopkins’ pace reduced his own ability to do anything but turn things into a grabfest at close quarters and a feinting match at a distance.

By the fight’s halfway point, Hopkins slowly had begun to finally look his age. He seldom was pulling the trigger, spending most of the time trying to smother Calzaghe by throwing one punch and then holding until Cortez would step in and break them up. Calzaghe, frankly, wasn’t doing anything special himself but he was landing more and, more importantly, now throwing more when he was not in the clutches of Hopkins, who would dive in with his head low and simply wrap his arms around Calzaghe’s waist.

“I wasn’t slowing down,’’ Hopkins insisted. “Freddie (Roach, his chief trainer) told me to pace myself.’’

That’s one way to look at it. Whatever his plan he remained difficult to hit cleanly, as he always has been, but his early lead seemed to have disappeared by mid-fight from his inability to muster any offense.

Calzaghe finally caught Hopkins with what he thought was a solid flurry late in Round 7 only to be countered at the final moment by a right hand that sent Calzaghe into a squat, momentarily stunned before he reeled back as the bell sounded to end the round without further damage.

The eighth round provided the best action of the evening since the opening round with Calzaghe landing effectively several times and Hopkins countering back. At one point, Calzaghe cuffed Hopkins in both ears but before he could move out of range he ate a counter right hand. Yet more and more often it was Calzaghe’s left that was getting in as Hopkins repeatedly retreated, often to the ropes to save his legs.

When the bell sounded to start the 10th round a telltale moment came, as Hopkins was still sitting on his stool, looking very much like someone in need of a longer break. A minute later he was on his hands and knees from what he claimed was a low blow. Although the replay did show Calzaghe had tapped Hopkins below the belt, Hopkins’ glove had blocked the shot. Yet he used the full rest period Cortez gave him and when it was over he seemed momentarily revitalized, landing more frequently but not often enough to win the round.

“He knocked my private parts outside of my cup,’’ Hopkins claimed. “That’s what made it hard.’’

That was not the case in Round 11 however. Once again Hopkins went down claiming a low blow and once again Cortez gave him a break, although this time a brief one. The difference was when the two began to engage again it was Calzaghe who got the better of it.

Landing two big flurries on the champion as Hopkins backed up, Calzaghe stopped and eyed Hopkins who hollered at him “Come on!’’ Come forward he did, as the crowd hollered. Although the fight had been a difficult one to score with many rounds a case of Calzaghe landing little and Hopkins barely at all, it seemed clear in the end that the old man was the beaten one. Not by a lot but by enough that there was a larger message there to Bernard Hopkins: time to stop before you get stopped.