PHOENIX — When the Celtics left Boston to start this five-game Western Conference road trip, they had rinsed away their bad start and started to resemble the team they hoped to become.
Five games later, though, they will return home humbled. They were dominated in their 111-90 loss to the Suns on Friday, just as they were dominated in long stretches of the games that preceded this one. Their 1-4 trip sunk their record back below .500, and it will ignite new questions about where this season, which is now one-third complete, is headed.
After this most recent loss, coach Ime Udoka made it clear that he now has enough of a sample size to assess this team, and that he will not be afraid to make some potentially significant alterations.
“We’ll look at everything based on these  games and see where changes need to be made,” Udoka said, “whether it’s lineup, rotation, minutes, everything.”
The eventual return of All-Star forward Jaylen Brown should help. Brown on Friday missed his fifth game in a row and 13th this season because of a hamstring issue, but Udoka said before the game that Brown has made substantial progress over the past few days and will likely return soon.
When asked about Udoka’s comments related to lineup and rotation changes, Celtics star Jayson Tatum agreed that it was deep enough into the season for a fair evaluation, but he also pointed out that Boston has rarely been whole.
“Obviously, the coaches, they’ve got to do what they think is best,” Tatum said.
Returning home to TD Garden would generally be an elixir, too, but in this case it just means getting a chance to face the Bucks and Warriors, two of the top teams in the NBA. The downward spiral could intensify rather quickly.
Nevertheless, Udoka said he is not concerned about losing the locker room. Just three games ago, after the Celtics throttled the Trail Blazers, Boston was clearly trending upward. He believes the team can regain that edge.
“I mean, literally three games ago we were playing a totally different style with the effort and the heart and intensity,” Udoka said. “So it’s been inconsistent, for sure, but it was just here, and it’s been here for most of the year.”
Even though the Celtics made some of their recent losses competitive by the end, they spent most of the time starting up at massive deficits. Friday’s game was the third in a row in which Boston trailed by at least 20 points.
Just like in Tuesday’s loss to the Lakers, Udoka waved a white flag by emptying his bench with more than five minutes left.
Yes, the Celtics were once again without Brown, and Josh Richardson sat out due to COVID-19 health and safety protocols. But the Suns were missing two of their best players in Devin Booker and DeAndre Ayton, so personnel issues are no real excuse.
“It’s completely on us as players to take ownership,” center Robert Williams said. “Put a stop to something if you don’t like it. Can’t blame it on anybody else.”
Tatum had 24 points on 10 of 25 shooting for Boston and Dennis Schröder added 15. But offensive highlights were few and far between. Marcus Smart’s shooting woes continued with a 1 for 13 night, and the Celtics made just 37.6 percent of their shots overall and 15.4 percent of their 3-pointers.
They trailed by two points after the first quarter but were walloped with a 25-3 second-quarter run during which nothing went right for them. Tatum and Smart combined to miss four free throws in a row at one point, and at the other end of the floor Suns centers JaVale McGee and Jalen Smith, who entered the night without a 3-pointer all year, hit two of them.
During that second quarter, the Celtics missed all 9 of their 3-pointers, committed six turnovers, and were outscored 32-15.
“I think it was kind of like a snowball effect,” Tatum said. “We let one turnover, one miss kind of build and build instead of moving on to the next play, and kind of let it carry over. And then I think our offense, we let that affect our defense, and they got rolling.”
Boston chipped away at a 24-point deficit and pulled within 12 in the third quarter. But that minor run provided just fleeting hope, as the Suns mostly shrugged and easily regained their massive lead when they felt like doing so.
“It’s tough losing three in a row,” Tatum said. “It’s tough, and especially coming in the fashion that they have. But we can’t change it, and we’ve just got to get back home.”