Before the Boston Celtics trekked north of the border for Tuesday's game against the Toronto Raptors, coach Brad Stevens was asked if he could pinpoint the reasons the Celtics have struggled so mightily against the Raptors in recent seasons.

"People struggle with them because they're really good," Stevens said.

Yes, the Raptors have given plenty of teams fits because of their obvious talent, but maybe no team more than the Celtics. During Stevens' four-year tenure, Boston is 4-10 against Toronto and has lost five of the past six meetings.

On Tuesday, a surging Boston team had a chance to shuffle into a tie for the No. 2 spot in the East with a Toronto squad that has been stumbling a bit. But despite the Celtics' owning a 16-point lead with a little more than 17 minutes to play, the Raptors rallied for a 114-106 triumph at the Air Canada Centre.

The Celtics couldn't cool off DeMar DeRozan in the second half, and he put up a season-best 41 points to go with a career-best 13 rebounds. Toronto big man Jonas Valanciunas scored 18 points and grabbed 23 rebounds, including 11 on the offensive glass, which reminded Boston that its size and rebounding deficiencies are still major concerns against top competition.

The Celtics are improving but still see themselves looking up at DeMar DeRozan and the Raptors. Tom Szczerbowski/USA TODAY Sports

A Celtics team that has routinely taken care of business against lesser foes this season -- Boston is 0-4 against the Raptors and Cavaliers but 13-3 versus the rest of the East -- looked a bit disheveled after the Raptors rallied Tuesday. It seems fair to wonder if there's a bit of a mental hurdle that these Celtics must overcome to truly compete with the Raptors.

The Celtics have three months to figure things out. As we near the midpoint of the 2016-17 season, playoff seedings are tenuous at best, but ESPN's Basketball Power Index gives both Toronto (65.5 percent chance at the No. 2 seed) and Boston (71.4 percent chance at the No. 3 seed) heavy odds to finish where they currently stand.

Although the Celtics still have to prove they can win a playoff series, BPI offers a 42.4 percent chance that Boston and Toronto will meet in the Eastern Conference semifinals. No other two-team matchup is nearly as likely (for instance, a Celtics-Cavaliers semis matchup has the next-best odds, at 21.2 percent).

Another loss to a quality foe will mean a rehash of Boston's struggles against good teams this season. Boston is 0-8 against the teams ahead of it in the league standings. The Celtics are still searching for a win against a truly elite opponent. Despite all of Isaiah Thomas' fourth-quarter wizardry lately, he couldn't rescue Boston on Tuesday.

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What can Boston do to ensure it can compete with a team such as Toronto in May?

Health : Having Avery Bradley, who missed his second straight game Tuesday due to an Achilles strain, back certainly wouldn't hurt Boston's ability to contain Toronto's All-Star backcourt. Marcus Smart played well in Bradley's starting role but is an obvious luxury in a reserve role where he can maintain Boston's defensive intensity as the starters go out.

Rebounding : When the Celtics were struggling at the start of the season, much was made about their lack of pure size and the way opponents dominated the offensive glass against them, leading to easy second-chance points. Rebounding hasn't been as much of a concern lately, if only because Boston had won 10 of 12 entering Tuesday's game, but recent losses to the Cavaliers and Raptors are reminders that Boston could use a strong rebounding presence. If Celtics president of basketball operations Danny Ainge can't hit a home run and fetch a superstar before February's deadline, he might be able to help the team's long-term future by finding a rebounding role player who can shore up one of Boston's most obvious weaknesses, even if just in a reserve role. You'll hear familiar names such as Andrew Bogut pop up, and Boston should pounce if the asking price isn't absurd.

Confidence: Entering play Tuesday, BPI predicted the Celtics to win 50.5 games, which would be nearly six wins more than is predicted for the Atlanta Hawks team projected to finish fourth in the East. Despite this stumble, Boston is the BPI favorite in nine of its next 12 games (and one of those underdog games is Friday in Atlanta, where Boston will have plenty of motivation to get Al Horford a win against his former team). More importantly, the Celtics have two more regular-season games against Toronto -- one on Feb. 1 in Boston and a second visit to Canada at the end of that month. Winning one of those games could go a long way if the two teams do indeed cross paths in the playoffs.

As Stevens has repeated often lately, the Celtics are not yet where they desire to be. Even in winning 10 of 12, there were obvious areas that needed improvement, including defense. Boston has plenty to tweak before the playoffs arrive.

It's prudent to not overreact to one loss on the road against a quality opponent, but Tuesday's loss is a reminder that Boston has work to do. The Celtics are still trying to claw their way onto the level of teams such as the Cavaliers and Raptors in the East.