SAN ANTONIO -- As Boston Celtics players dressed quietly in another hushed locker room following their latest defeat -- a 108-101 loss to those ever-executing San Antonio Spurs on Wednesday at AT&T Center -- forward Jae Crowder sat expressionless at his locker, two feet plunged deep into a mop bucket filled with ice that did little to stop the obvious frustration dripping from his body.

Crowder does not consider himself blindly optimistic when he suggests the Celtics have shown encouraging progress lately. But you can tell he's tired of trying to explain Boston's inability to win games against quality opponents.

So given the opportunity to accentuate the positive, Crowder was brutally honest in his postgame assessment of this Celtics team.

"We’re showing progress. We watch a lot of film and we see we are getting better," Crowder said. "As a player, you get to thinking like, how long are we gonna talk about that? I’m ready to see some wins and I’m willing to do whatever it takes to get wins against top teams."

The Celtics dropped their third straight game with Wednesday's national TV loss to the Spurs, the only team that coach Brad Stevens has not beaten in his four-year NBA tenure. Boston has lost to some very good competition over the past nine days: the Spurs, Thunder, Raptors and Rockets. What's more, All-Star point guard Isaiah Thomas was either out or hampered for that entire stretch (he has missed the past four games after injuring his groin in the first half of the loss in Houston).

But Crowder refused to sugarcoat this latest defeat. Asked about the Celtics' frustration level, he replied simply, "Pretty high." It was noted that Boston is barely above .500 through 25 games and Crowder was asked where Boston stands.

"We’re still trying to figure it out," he said. "Haven’t got there yet, obviously, and it shows in games like this. From top to bottom, we just haven’t figured it out."

Crowder said that, despite Boston's struggles, players remain positive with each other and there have been no obvious signs of finger-pointing. Pressed on what Boston needs to figure out, he declined to get too specific.

"It’s not one thing. It’s a few things that we have to figure out. We keep those things in-house," Crowder said. "Health is one [problem]. Just us being on the same page, all five guys on the same page at one time [is another]. There’s a lot of big things we could pinpoint that’s holding us back right now."

Celtics players lamented how the typically composed Spurs were able to withstand Boston's charges and respond with a run of their own that kept Boston at arm's length. Each time Boston made a miscue, San Antonio pounced and kept pushing its lead out.

"We're still trying to figure it out," Jae Crowder said. "Haven't got there yet, obviously, and it shows in games like this" against the Spurs. Soobum Im/USA TODAY Sports

"I've said the last couple of days that we've made progress. I didn’t think we played as well [Wednesday] as we did in Oklahoma City or maybe even at home against Toronto, but [the Spurs] had a lot to do with that," Stevens said. "And every time that we got within striking distance, Kawhi Leonard made a huge play or they came up with a loose ball or an offensive rebound. They're tremendous at maximizing every detail of the game. And, you know, hey, we've had our moments where we play really well, but we're not as good as them at that."

Stevens certainly believes his team has the potential to get to a level comparable to some of the elite teams in the league, but Boston is far from that destination at the moment. The absence of Thomas hasn't helped, particularly as the Celtics have endured painful scoring droughts in key situations, but it's far from the only issue this team is dealing with. Even with Thomas, the Celtics haven't produced a truly defining victory this season.

This team is hopeful that, with Thomas expected back for Friday's visit by the Charlotte Hornets, it gets a much-needed jolt. A win against a quality opponent could go a long way toward relieving a team that's quite clearly pressing and not simply playing clear-minded basketball.

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The scarier thought is what happens if Thomas returns and Boston still fizzles. For now, this team is staying optimistic despite the frustrations.

"Once we’re able to put together a whole game, I feel like we’ll get back to playing the right way," Avery Bradley said. "And especially adding Isaiah, he’ll be able to help us out, of course, on both ends of the floor as well. We just need to move on to the next one, not have our heads down. We played a very good team tonight and we did do some great things tonight. All we can do is build off those great things and let it carry over to the next game."

Echoed Marcus Smart: "You’ve got to just move forward. You’ve got to move on. You’ve got to train yourself to knock these games out just like you do the good games. These bad games, you’ve got to let them go because you play again soon. So that’s the part of being a professional, and that’s part of the reason why everybody’s here. Their whole career they’ve been real good at being professional about it and doing those things."