Whew, what a day.

Five trades went down in the 24 hours preceding Thursday’s NBA trade deadline, involving ten teams and 25 players — after we’d already seen an already unprecedented flurry of deals in the early part of February.

Blame it on Pau Gasol. Contending teams keep trying to upgrade their rosters in an arms race that started three weeks ago when the Lakers pried the Spanish 7-footer loose from Memphis. Since then we’ve had several whoppers, including the Nets’ trade of Jason Kidd to Dallas and Phoenix’s acquisition of Shaquille O’Neal.

Fittingly, the swap meet closed with another monumental exchange. In a three-team, 11-player swap that also involved Seattle and Chicago, the Cavs shipped out disappointing guard Larry Hughes, power forward Drew Gooden, and four guys who were out of the rotation. In return, they got four-time Defensive Player of the Year Ben Wallace, power forward Joe Smith, sharpshooter Wally Szczerbiak, and scoring guard Delonte West.

On their own, none of these four players would send knees shaking around the Eastern Conference. Wallace has declined rapidly since signing a huge free-agent deal with the Bulls, Szczerbiak is a moderately productive scorer but a defensive liability, Smith is a middling talent at power forward, and West is a shooting guard in a point guard’s body.

But throw them all at once into the current Cleveland stew, and it could be quite a combination. Let’s start with the big picture: The Cavs already have the best player in the game in LeBron James, who leads the league in Player Efficiency Rating (my measure of a player’s per-minute effectiveness) by a wide margin and has carried his underperforming supporting cast all season. They don’t need the other guys to be awesome — they just need “decent.”

Thus far, only two Cavs have qualified: Center Zydrunas Ilgauskas, who is quietly putting together another high-quality season, and reserve big man Anderson Varejao, a defensive force who makes tons of energy and hustle plays.

After that, it gets dicey. Point guard Daniel Gibson is a great 3-point shooter (47.6%) but pretty much a zero in other areas; starting wings Hughes (37.7%) and Sasha Pavlovic (35.5%) have been comically inaccurate shooters; and Gooden has had an off year after a very solid campaign the season before.

The net result is that replacing these guys with even average players does wonders for the Cavs. Szczerbiak can’t guard a toaster, but his long-range shooting will be a night-and-day shift from Hughes’s bricks. West is a middling shooter with the grating habit of letting his man beat him off the dribble and then trying to block the shot from behind, but he can’t possibly be worse than the motor-mouthed Mohawk known as Damon Jones.

It’s similar up front. Wallace’s best years are behind him, but compared to the injury-plagued Marshall or the extremely limited Dwayne Jones, he’ll be an improvement. And then there’s Smith, whose smooth 17-footer should be a major asset on a team starved for shooting, and whose mental game should be a big upgrade on the gaffe-prone Gooden.

Suddenly, the Cavs have a four-man frontcourt rotation of Ilgauskas, Smith, Varejao, and Wallace that rivals any in basketball. They have big-time shooters in Szczerbiak and Gibson. They have a guard who can create shots in West. And they can match up against small lineups by playing James at power forward and Szczerbiak at small forward.

Does it make them a contender along the lines of Boston and Detroit? I’m not sure if I’d go there yet. For starters, the Cavs’ 30–24 record is a bit deceptive — they have been outscored in the season by 1.2 points per game, which normally would put a team a couple of games under .500 rather than six games over. So there’s a lot of work to be done.

However, they may be better than that mark indicates. They lost the six games James missed by a combined 68 points — take them out and they’re victory margin goes back to even. And they’ve played much better defensively with Varejao in the lineup. He didn’t re-sign until December after a contract dispute and went out again in late January with an ankle sprain. But when both James and Varejao play, the Cavs are 15–7.

Varejao will be back in the lineup soon, and he’ll have a lot more company this time. Seen in that light, one wonders if the upgrades can allow the Cavs to go shot for shot with the East’s powerhouses. On paper, at least, it seems stronger than the Cleveland team that ate Detroit in the conference finals a year ago, so it’s not great a stretch to suggest they could do it again.

While the Cavs went for the home run, other contenders opted to work around the edges. San Antonio got a much-needed frontcourt boost by acquiring ex-Knick Kurt Thomas from Seattle in return for Brent Barry, Francisco Elson, and a 2009 first-round pick. While he’s getting up in years, Ol’ Crazy Eyes can still stroke it from 15 feet and play tough post D. Those were essential needs for the Spurs given how much Robert Horry’s play has tailed off this year.

Division-leading (!) New Orleans also got into the fray, upgrading its suspect bench by trading Bobby Jackson to Houston for Mike James and Bonzi Wells. Wells gives the Hornets a much-needed low-post scorer, and a quality backup at the wings should Peja Stojakovic’s creaky back start acting up on him again.

In the East, Detroit jumped in with a minor deal, swapping Primoz Brezec for Juan Dixon to get some additional insurance in the backcourt.

Alas, two Eastern teams steered clear of the fray: The Knicks and Nets. New York had been shopping to deal Zach Randolph, but his questionable character and huge contract combined to scare off most suitors.

Across the Hudson, Rod Thorn couldn’t get anything started — much less finalized — in talks involving Vince Carter, so he’ll likely give it another shot before draft day. Carter’s rep has taken an unusually large hit this year, but if he has more 33-point, nine-rebound, seven-assist games like he did in Wednesday’s win against Chicago, Thorn’s job will become a lot easier this June.

jhollinger@nysun.com