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How Trevor Ariza Makes a Difference in Portland (or not)

Portland got a new small forward and all of a sudden started winning. Does correlation equal causation?

NBA: San Antonio Spurs at Portland Trail Blazers Soobum Im-USA TODAY Sports

The Portland Trail Blazers have been playing some of their best basketball of the season. Coinciding with their hot stretch has been the arrival of small forward Trevor Ariza, who immediately earned praise when he stepped into Portland’s starting lineup ten games ago. What exactly is Ariza doing and how is it making a difference...or is it at all? That’s fodder for today’s Blazer’s Edge Mailbag.

Send your own Mailbag questions to if you want them answered!


Ariza has been great for us. Seriously great from what I see! Can you talk about how it’s different now and what he’s doing to make such a big difference?


Trevor Ariza has been great for the Trail Blazers in two specific ways. We need to be careful about conflating those gifts with winning percentage, though. Correlation is not causation.

Ariza has helped Portland’s defense. He’s the first person on this year’s squad willing to take on the challenge of defending the best opposing scorer (and capable of doing a credible job of it). Neither the starting guards nor Carmelo Anthony have the tools. Hassan Whiteside doesn’t have the instincts or mobility. Ariza gives the Blazers the “Al-Farouq Aminu” defensive bulwark they lacked before he arrived.

Whether guarding a high scorer or not, Ariza is capable of sealing off an area of the floor. Defense isn’t just about stopping buckets. NBA teams routinely score 100+. Nobody really gets stopped. Instead defense wants to shave percentage points off of the opponent’s shooting. This happens when defenders are within closing distance of shooters. The critical defensive edge comes when defensive players can predict where they need to be on the floor and then get to that spot.

The easiest way to predict where a defender will be most useful is to narrow down the options. Any player who has to cover five different spots at once is going to get beat by the offense. Acting is always quicker than reacting. Narrow down the potential destinations to three and the defense automatically gets better.

Ariza is able to contain offensive players in whatever area of the floor he patrols. This allows his teammates to narrow down the areas and players they have to plan for. You may have noticed that Anthony looked ineffective when stuck out on an island, having to watch 360 degrees around him. Lately he’s been getting into passing lanes and cutting off drives before they happen. He didn’t all of a sudden get better. Knowing what’s sealed off behind him, he knows the extent of his own responsibility. He’s able to do more—more accurately predicting where he can be of value—within that defensive area.

The same is true, in general, of Whiteside. You don’t see him flailing out around the three-point arc as much, completely ineffective and out of the play. He can patrol a smaller space, filling it to greater effect.

That said, Ariza has not been a cure-all. The Blazers currently allow 114.9 points per game, 25th in the league. That’s actually worse than the 114.1 (23rd ranking) they were allowing before he arrived. Similarly, Portland is currently allowing opponents 44.8% shooting from the floor, slightly worse than the 44.5% rate before Ariza arrived. More egregiously, they’re ceding 37.1% from the arc, up a full percentage point from the 36.2% allowed in pre-Ariza days. Opponent free throws attempts have improved from 25.3 to 24.6. Otherwise, the Blazers are not better, and may actually be worse in some areas, with Ariza on board.

(All stats were taken on the afternoon of February 10th. The Blazers giving up 138 points, 53.3% shooting from the field, and 41.2% from the arc to the New Orleans Pelicans last night did not improve the picture.)

Ariza’s second great asset is shooting 40% from the three-point arc on 3.3 attempts per game for the Blazers. That’s considerably better than his 35.2% mark with the Sacramento Kings earlier this year. It’s light years ahead of Kent Bazemore’s 32.7% rate with the Blazers on nearly the same number of shots.

40% shooting from the arc is a little bit of a magic number. Centers ruled the NBA in the days when rules favored physicality. Teams worked to get the ball inside to their big men, earning the highest percentage shots possible. The gold standard for centers was 60% shooting. If your big man topped that mark, you were getting the best production possible.

Shooting 40% from the three-point arc produces the exact same number of points per shot that shooting 60% inside does. When your wings hit that mark, they are scoring as efficiently as anyone could hope for, give or take a super elite center or an even better three-point shooter. That’s what Ariza is doing for the Blazers right now.

There’s no doubt Ariza’s shooting helps Portland. Guards don’t have to hesitate passing to him on the wings the way they might have with his predecessors.

Again, there’s a caveat. Ariza is scoring 11.7 points per 36 minutes. That’s not a bad number considering he’s the fifth option among the starters. Bazemore averaged 11.0, though. The increase isn’t dramatic.

In no way do the asterisks belittle Ariza’s contributions. He’s a better fit than Bazemore. He might prove better than Al-Farouq Aminu was in the long run.

Still, Ariza is not the reason the Trail Blazers are winning games right now. He’s appeared in 10 games so far for Portland. Damian Lillard has scored 30+ in 7 of those 10. The Blazers are 5-2 in those 7 scintillating Lillard performances. They’re 1-2 when Lillard has failed to reach that mark.

Ariza is making a positive impact; Dame is turning impact into wins. Without Lillard scoring high, Portland’s permissive defense would have cost them games, with or without Ariza.

It’ll be interesting to see how this all settles out as the season winds down. I expect Ariza will continue to integrate. If the Blazers make the playoffs, their opponent will no doubt prefer to see if Portland can win via Ariza’s shooting rather than via Lillard’s scoring. Both he and the team will need to answer that challenge, as well as the challenge of defending elite Western Conference stars.

For now, the Ariza trade looks good. It’s not the main reason Portland is winning. Whether it ultimately changes anything remains to be seen.