By Matthew Geagan, CBS Boston

BOSTON (CBS) — The Celtics have a true test on their hands Wednesday night at TD Garden. Boston, winners of six of their last eight games, welcome in the Indiana Pacers, who have won seven of their last eight.

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It’s a great opportunity for a Celtics team that appears to have turned a corner to prove that they have, indeed, turned a corner. The Pacers are a legit threat in the East, and a win on Wednesday would be one of Boston’s best of a rather disappointing first half of the season.

While all the preseason hype went to the Celtics and Toronto Raptors in the East, Indiana has propelled themselves into the conversation with a great start to the season. They’ve followed up last year’s 48-34 campaign with a 27-13 start to the season, currently seated in the No. 3 slot in the Eastern Conference.

They’re doing it with some stellar defense, as Nate MacMillan’s team is second in the NBA with a 103.4 defensive rating. The Celtics currently rank third at 104.1. Juicy.

Indiana has a stud scorer in Victor Oladipo, who has added some clutchness to his two-way game this season. That was on full display when the two teams met back on Nov. 3 in Indy, when Oladipo drained a game-winning three with 3.4 seconds to go. He had 24 points and 12 rebounds in that contest, and will be a handful for Marcus Smart once again Wednesday night.

“It’s going to take all five guys on the court. He’s a great player and they have a great team,” Smart said of guarding Oladipo following Monday night’s win over the Nets. “They do everything the right way; they’re in the right spots on defense and offense. We just have to make it real tough on them and can’t let them come in and be comfortable.”

The Pacers have won three straight over the Celtics, with Oladipo scoring 35, 27 and 24 points in those contests. He has a solid supporting cast with the likes of Domantas Sabonis (14.9 points, 9.6 rebounds per game), Bojan Bogdanovic (16.5 points per game on 47 percent shooting), and veteran Thaddeus Young. Even when Oladipo missed three weeks with a sore right knee, the Pacers won seven of their 11 games without his services.

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But where the Pacers are vulnerable is from downtown, with opponents hitting 36 percent of their attempts from deep. In Indy’s loss to Toronto on Sunday, which snapped a six-game win streak, the Raptors hit 17 of their 33 attempts from three-point land. That should have the three-happy Celtics salivating.

If their first meeting of the season was any precursor, Wednesday night should be quite the entertaining affair. Back on Nov. 3, there were 10 ties and 18 lead changes. Kyrie Irving and Oladipo engaged in an entertaining battle, with Irving scoring nine of his 18 points in the final quarter. His three with 38.1 seconds left gave Boston a 101-97 lead, but he missed a layup with 11 ticks remaining on the clock with the Celtics up two, setting up Oladipo’s heroics.

Hopefully, Oladipo vs. Irving Round 2 is just as exciting.

But both teams are different from the ones we saw in that first go-around, especially in Boston. Jaylen Brown and Gordon Hayward are no longer in the Boston starting five, replaced by Smart and Marcus Morris. Morris has provided some grit to the C’s lineup, and Smart has actually turned himself into a fairly decent shooter from downtown. Sabonis is now in the starting five for Indiana, and is the kind of versatile big man who has been giving Boston fits this season; he had 12 points, nine rebounds and five assists in their first meeting.

The Celtics of late have shown signs of being the team we all expected them to be before the season started. But they’ve done that before this season, and any time it appears they’ve figured things out, they revert back to the frustrating team that can’t slow down their opponent or hit an open shot.

It’s a trend that needs to end with the midway point of the season approaching.

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“Every game now, we’ve got to look at it as a big game,” Smart said Monday. “Every game counts. We’re working for something much greater. We’ve got to continue to be great and progress in the right way, instead of decline.”