Today’s the biggest game of the year, to date.

Never mind what Lebron James said about the Heat having no true rivals. Never mind that playing Los Angeles was a rematch of The Series That Must Not Be Named. Never mind that Orlando felt like such an important contest, with elbows and shoves being handed out like free samples. It’s getting to be that time of year when the standings count. The Celtics are now 1/2 game behind Miami for the East’s number one seed, a seed that comes with homecourt advantage. A win today would put Boston back in the lead, and would also give them something that could come in handy down the road — a tiebreaker, in case the two teams finish the regular season with identical records.

Beyond that, Boston has a chance to crane kick Miami’s psyche. Beating them once was nice. But it was Miami’s first game together. Beating them twice was nicer. But it was just one game. Beating them a third time — without all three backup centers, and without Marquis Daniels, and without Delonte West — would have to make Miami wonder: “Can we beat these guys?” Once is an accident, twice is a coincidence, and three times is a pattern.

Lebron James hardly knows what it feels like to win in Boston. In the Big Three era, Lebron has played in Boston 13 times. He’s won once. It’s not all Lebron’s fault. He averages more than 31 points per game against Boston, the most any opponent has ever averaged against Boston. But it has to be somewhere in the back of his self-loving mind: “What do I have to do to take these guys down?”

Miami obviously has talent, oodles of it. Only two questions surround Miami this season:1) Is the supporting cast — what with Mario Chalmers and Zydrunas Ilgauskas in the starting lineup — enough? And 2) Can the Heat execute in crunch-time, playoff-type situations? The answers to both questions, in meetings one and two with Boston, were no. But the Heat feel like times have changed. (Miami Herald)

“We were a totally different team the last two times we played the Celtics,” Heat forward LeBron James said. “Those guys were just too much for us at the time – very overwhelming for us at the time – and we’ve come a long way. We just need to show what we’ve [been] doing as of late and take it to the game on Sunday.”

But the Heat aren’t going to measure themselves against any other teams. They’re going to measure themselves against Boston, because the Eastern Conference goes through Boston. If, after becoming “a totally different team,” Miami’s still overwhelmed by a shorthanded Celtics squad, the Heat’s eight straight wins heading into today’s matchup hardly matter.

Boston tests opponents in ways no other team does. The Celtics rattle you. They play team basketball, and they throw elbows, and they make the extra pass, and they refuse to back down no matter what happens. They talk a lot of junk, and they stand their ground, and they have a handful of future Hall of Famers surrounded by a few solid role players, coached by the perfect (for their outfit) manager. They won’t ever give you a game. They make you rip it from their hands, as they clutch onto it with a grip of death.

“Now the target is on our back,” said Erik Spoelstra of today’s matchup, because his team sits in first place in the Eastern Conference standings. But let’s be serious, Erik. The Celtics know they can beat Miami. The target’s in the same place it has been all season, on the backs of the defending Eastern Conference champions.

More accurately, there are two targets. Both teams need today’s win, badly. The Celtics, to snap a brief losing skid, get back on track, and regain first place. The Heat, to validate what they consider improvement. There are very few regular season games that actually hold long-term significance. Enjoy today.