Celtics’ confidence takes a beating

Avery Bradley (2-of-5 shooting, 6 points) couldn’t get going against Wesley Matthews and the Blazers. Barry Chin/Globe Staff

In case you’re wondering, the answer is yes, this is how this Celtics’ season is going to transpire. It will be filled with ups and downs, soaring confidence and bewildering disappointment, virtual certainty and mass confusion.

Friday night offered more of the negative. The Celtics were dusted by the Portland Trail Blazers, 109-96, at TD Garden, a rather predictable loss to a better team. Portland has gone through a series a rebuilding projects and appears ready to take the next step, and the Trail Blazers showed enough poise to stave off Boston rallies and pull away.

Just four days after winning their fourth straight game, the Celtics are in another quagmire. They begin a difficult three-game road trip to Minnesota, Houston, and San Antonio, then return home to face undefeated Indiana.

Again, the Celtics are wondering where they will notch their next win just a few days after Brad Stevens was unofficially named NBA coach of the week after four straight wins, which occurred after four straight losses, or grab the early lead on the Randle-Parker-Wiggins sweepstakes.

Having shown the ability to win, play consistently in stretches, and beat one of the NBA’s top teams on the road — Miami — the Celtics have raised expectations. But they are putting themselves through emotional turmoil with their maddening inconsistency, which is not surprising.

Mediocre or below mediocre teams aren’t always ghastly to watch. They are capable of playing well for extended periods, but mental miscues and struggles with execution are never too far away. The Celtics experienced that Friday when they shot nearly 46 percent — even after a 6-for-21 fourth quarter — and performed well enough offensively to win.

Yet, they could not offer any resistance to LaMarcus Aldridge, who took advantage of a lack of a counterpart for 27 points and 12 rebounds. They couldn’t defend the 3-pointer at critical moments, allowing the Trail Blazers to attempt 26 and hit nine.

Just when the Celtics believe they are vastly improving, have solved their defensive woes, and are beginning to find a way to score easier baskets, they collapse in one of those categories. In Wednesday’s loss to Charlotte, they were inept offensively but solid on defense.

It was the opposite Friday, which can be maddening for a neophyte coach like Stevens. But Stevens refused to buy into the short run.

“More topsy-turvy for everybody else than it is for me,” Stevens said. “I hate losing. I don’t stomach it well. I don’t deal with it well but I’ll be back at work tonight.”

When asked how the players deal with the inconsistency, he said, “They’ve got to handle that. And we’ll talk about it. It’s a long season for everybody. Everybody’s going to have ups and downs and rounds and rounds. So you’re going to have to manage it and try to be as good as you can be tomorrow. It’s just like we talked before. There’s no time to sulk. The stretch we’re about to go on is as tough as it gets.”

So it’s critical for the Celtics to remain mentally consistent and confident. Bad teams are bad because inherently, they know they are bad, they become tense in crucial moments, waiting for the next mistake to occur. The Celtics can’t get in the habit of believing they are destined to lose, and long losing streaks can encourage such thinking.

It’s difficult to be as calm as Stevens has been but in this case, his players have to pattern themselves after their coach.

“You definitely want to tell the new players that it’s going to be like that,” guard Jordan Crawford said about the NBA’s mood swings. “It’s a long season. All of sudden we just won four, all of a sudden we’re losing two. We’re just looking for a win, so tell everybody not get too high, not get too low, just keep getting better every day.”

It sounds like a cliche, but it’s accurate. The Celtics have to begin to develop an identity. The overall improvement of the team has been obvious through 10 games.

Gerald Wallace has warmed to his bench role. Avery Bradley has become more productive at shooting guard, and Crawford is capable of playing point guard. None of those were apparent when the season began. Wallace was a starter, Bradley was the point guard, and Crawford was a shooter off the bench.

There is development occurring, and during their four-game winning streak, the Celtics felt they were capable of playing with any team. Two losses can’t discourage that, especially when every team besides Indiana has taken turns looking terrible.

“It’s the NBA, it’s a lot of games,” guard Courtney Lee said. “There’s nights you’re going to have games where shots don’t fall, there’s going to be nights where other team’s shots are falling. You can’t get too down. We got another game tomorrow.”

The NBA requires a short memory and the Celtics have to gain mental fortitude if they plan to make it through a roller coaster season as smoothly as possible. The first 10 games have already been a test of their patience.