The Senators will likely be without top defenceman Jake Sanderson for the final two games of the road trip

It didn’t take long for the Ottawa Senators’ depth on defence to be put to the test.

The Senators will likely be without top defenceman Jake Sanderson for the final two games of the road trip. It’s believed he was sent back to Ottawa on Sunday to undergo further testing on an undisclosed lower-body injury.

That means Sanderson, who left the club’s season-opening 3-2 victory over the Toronto Maple Leafs on Saturday at Scotiabank Arena, won’t face the Boston Bruins on Monday night at TD Garden or the Detroit Red Wings on Tuesday at Little Caesars Arena.

Sanderson aggravated a lower-body injury he suffered in the club’s final preseason game a week ago against the Montreal Canadiens.

He got caught up along the boards with Toronto winger Nick Paul in the first period against the Leafs and stayed on the bench for the remainder of the first period, but took only four shifts.

He wasn’t on the bench for the second period.

Sanderson is out indefinitely and was clearly frustrated with the setback.

“It sucks. You feel for a guy. I’ve been on that side of things quite a lot over my career, and he was devastated in the first when he told me on the bench,” said Ottawa captain Thomas Chabot, who had a goal and an assist in the victory over the Leafs.

“There is one thing for sure with Jake, he’s going to put everything into it, and he’ll be back in no time.”

The club didn’t skate on Sunday in Boston, but coach Travis Green told reporters in Toronto that Sanderson took himself out of the game.

“We’ll know more in the next few days, but Sandy was smart enough to pull himself early enough that he didn’t reaggravate it too badly. He just felt that it was coming and took himself out,” said Green. “That was a smart thing to do.”

Because Sanderson reinjured an ailment he was already dealing with, the Senators will take extra precautions this time.

Green will likely update Sanderson’s status following the club’s morning skate on Monday at TD Garden.

While Sanderson didn’t suit up in any exhibition games until he faced the Habs, Green told reporters last week that the ailment Sanderson left with against the Habs was different from the one that hampered him during the first week of camp.

Sanderson skated three straight days before being given the green light to return.

“It’s sh–ty right now, but I know he’ll be back soon,” said Chabot.

Sanderson’s absence means the Senators will face two Atlantic Division rivals without their top defensive pairing. Blueliner Artem Zub, who missed all of camp with a knee injury he suffered in the playoffs against the Carolina Hurricanes, isn’t on the trip.

Zub skated with his Ottawa teammates for the first time on Friday while wearing a yellow non-contact jersey. He’s closing in on a return, but there is no timetable for him to make his debut this season.

Veteran blueliner Cam Crotty is on the trip, and the expectation is that he’ll face the Bruins on Monday at 7:30 p.m.

Steve Staios, the club’s president of hockey operations and general manager, will likely have to recall another blueliner from the club’s American Hockey League affiliate in Belleville to be available for the final two games.

The Senators used 13 defencemen last season and made the playoffs, but the loss of  Sanderson and Zub presents a major issue.

“They’re thin back there already,” a league executive told the Ottawa Citizen on Sunday.

You have to wonder if the Senators will revisit their decision to release veteran defenceman Ben Hutton from his professional tryout last Tuesday. The club opted not to offer him a contract, but was open to having him skate with Belleville.

We don’t believe Hutton, 33, who has more than 500 games of NHL experience, had any interest in biding his time in Belleville. But it’s apparent now that the Senators could likely use a veteran like Hutton, unless Staios opts to go the trade route.