By Brian Robb, CBS Boston

BOSTON (CBS) — Last season, the Celtics managed to win just four games against Western Conference opponents. Wednesday night’s win over the title-contending Memphis Grizzlies gave the 2014-15 Celtics 12 victories (and counting) on the year against teams from the NBA’s superior conference.

There are many statistics that could illustrate just how much progress has been made in year two of the Celtics rebuild under Brad Stevens, but there’s no better place to look than that. Wednesday’s hard-fought 95-92 win over the Grizzlies should be highlighted as the best of those efforts.

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The Celtics came into the game shorthanded on a variety of fronts. Arguably the team’s two best players, Isaiah Thomas (bruised tailbone) and Jared Sullinger (fractured foot), were sidelined. On the size front, they had no one who could match the height of Marc Gasol, or muscle of Zach Randolph. It was Boston’s third game in four nights.

Ultimately, none of those excuses were needed, since the Celtics overcame all of them.

Phil Pressey stepped in with some serviceable minutes off the bench in place of Thomas. Brandon Bass, Tyler Zeller, Kelly Olynyk and Jae Crowder all took turns frustrating Randolph and Gasol, as the duo combined to score just 25 points on 22 shot attempts. After the game, Stevens raved about his team’s defense against the pair, as he used strategic double teams all night to keep both off balance.

“Our bigs played really hard. They played really well. [Gasol and Randolph] are a former All-Star and an All-Star starting center. Felt like we had to do that. Tony Allen cut us up as a result of some of the double-teams in the second half, so that’s why we had just (Brandon) Bass and Tyler (Zeller) in there as much as possible late to just try to play them one-on-one,” Stevens said.

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With the win, the Celtics have now won four of their last five games, seven of their last 10, and 14 of their past 24 overall. The victory was aided by the return of Avery Bradley, who returned from a three-game absence due to a left elbow injury to score 17 points. However, beating a healthy contender like the Grizzlies without the help of Thomas and Sullinger was a big confidence booster for the C’s.

“It means a lot for us,” Bradley said after the game. “Even winning those two games we won on the road, we get a chance this Friday to go up against a team that beat us and get our revenge. It’s a blessing, that’s the best thing about the NBA – you get a chance to go up against another great opponent and go out there and get a win, prove that you’re improving as a team, improving as individuals. We’re definitely showing that everyone’s improving.”

“Right now, we’re going down the stretch towards the end of the season so we know every game counts,” Jae Crowder added after scoring 16 points off the bench. “We had a soldier down, so we had the guys step up tonight.”

The number of wins over quality opponents has been a growing list as well for Boston. Memphis, Atlanta, New Orleans, Phoenix, and Portland are all .500 or better teams that the Celtics have beaten in the past six weeks alone. With the playoff race heating up (Celtics trail Miami by 1.5 games), this upstart group is showing it won’t be an easy pushover if it sneaks into the bottom half of the East playoff picture.

“We’ve been in every game, except the Cleveland game, after All-Star Break, so it shows that we’re making strides and we’re continuing to be a better team,” Bradley said. “I think it all starts from Brad. Brad is getting us all together, having us believe in one another, we’re like a family out there. We’re a lot closer than we were, and it shows on the court.”

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Brian Robb covers the Celtics for CBS Boston and contributes to NBA.com, among other media outlets. You can follow him on Twitter @CelticsHub.