TORONTO -- For the Ottawa Senators the help comes now, for the Toronto Maple Leafs it comes later.

A mammoth nine-player swap between Ontario rivals Tuesday saw Leafs captain Dion Phaneuf land in the nation's capital in a trade that props up a mostly inexperienced Ottawa defence while shedding Toronto of another core player and his long-term contract, one that carries a US$7-million annual salary-cap hit and expires in 2021.

"I think both parties ended up where they want to be at this moment," Senators general manager Bryan Murray said of the trade. "We'll see now how it works out."

Phaneuf, at the very least, upgrades the Senators' back end as they race to catch up in the Eastern Conference playoff race. The 30-year-old instantly adds experience, penalty-killing acumen and some offensive capability to an Erik Karlsson-led group that features four defenders with less than 300 games of NHL experience.

Phaneuf recently played his 800th career NHL game, a total that far surpasses any of his new teammates on defence.

Murray had been looking for a left-shooting defenceman to play on one of his top two pairs, a hole that Phaneuf immediately fills. He's expected to play alongside 22-year-old Cody Ceci when the Senators visit the Detroit Red Wings on Wednesday night.

"He'll just bring, we hope, a presence to this organization," said Murray. "We don't expect him to come in here to be a saviour. We expect him to come here and just be the hockey player he is."

Phaneuf was enjoying one of his better seasons as a Leaf, a redemptive one in many ways following a challenging 2014-15 season which saw him finish with just 29 points. The Leafs, in a likely attempt to prop him up for just such a trade, were employing their captain in less strenuous duties under new head coach Mike Babcock. Phaneuf was no longer matched up against top lines, killing fewer penalties and getting more looks in the offensive zone.

On pace for nearly 40 points and averaging 22 minutes per game, Phaneuf will get a fresh start with his third NHL team, all of them Canadian.

"Dion's ready now to win and we're not ready to win," Babcock said. "It was a hard decsion. I think it's a good decision for Dion."

Beyond the injected experience, the Senators have to hope that Phaneuf helps them defensively. They surrender a league-high of more than 33 shots per game and yield more than three goals nightly, the third-worst mark in the league.

Murray said he hoped the trade would help Ottawa contend for the playoffs not only this spring, but beyond.

"At the end of the day we're in a business that is about winning and all I'm trying to do is help the Ottawa Senators be a winner," he said.

Ottawa sits four points back of the New York Islanders for the final wild card spot in the East.

The trade ends Phaneuf's turbulent run in Toronto, which began with a similar blockbuster swap six years ago, one that sent the former first-round pick to the Leafs from the Calgary Flames. Phaneuf had been Toronto's captain since the summer of 2010, a period during which the club qualified for the post-season only once.

The key to the deal for the Leafs was cap flexibility. Toronto is trying to clear its deck of long-term pieces that don't fit for the future as it aggressively rebuilds through a revamped system of draft and development.

Phaneuf was in the second year of a seven-season pact worth $49 million, inked by a previous management regime on Dec. 31, 2013.

He's the second core player with a long-term contract to be unloaded by the Leafs' relatively new leadership group steered by team president Brendan Shanahan and general manager Lou Lamoriello. The Leafs started seriously deconstructing that core roster last summer when Phil Kessel was dealt to Pittsburgh for a package of prospects and draft picks.

Unlike the Kessel deal, which saw the Leafs retain $1.2 million annually until 2022, the Leafs kept no salary in the Phaneuf transaction.

"This is a transaction that certainly wasn't for today," Lamoriello said.

The deal cleared up significant cap space for the next five seasons, especially crucial for the club when a promising group of young players and prospects need second NHL contracts, Lamoriello noted. Morgan Rielly, the team's talented 21-year-old defenceman and impending restricted free agent, is due for one this summer.

Lamoriello saw no limit to the flexibility the transaction would provide.

"I don't think there's any letter in the alphabet left out. I think it's A to Z," Lamoriello said. "Whatever opportunity there is to make the Maple Leafs better certainly will be considered."

The Leafs have a series of expiring contracts that are likely to be dealt ahead of the Feb. 29 trade deadline. None, however, have the financial weight of Phaneuf's.

After consulting with Babcock, Lamoriello said the Leafs wouldn't name a captain in Phaneuf's absence.

The GM raved about Phaneuf, describing him as a supportive presence during the organization's transition this fall, which included Lamoriello as the new GM and Babcock as the new head coach. He told Phaneuf as much when the two spoke by phone after the trade was completed.

"He understands what we're doing here," Lamoriello said of the team's rebuilding plan. "He was just outstanding. I just can't say enough about him."

In addition to salary-cap relief, the Leafs added a former first-round pick in defenceman Jared Cowen, who struggled to find his way in Ottawa, along with slowing 31-year-old winger Milan Michalek, a second-round draft pick in 2017, 28-year-old AHL forward Colin Greening and 20-year-old prospect Tobias Lindberg.

The contracts of Cowen, Michalek and Greening all expire after next season.

Lamoriello said that Lindberg, a six-foot-three Swedish winger who had 22 points in 34 games for the Binghamton Senators, was the club's targeted prospect in the transaction.

Ottawa also received AHL forwards Matt Frattin, Casey Bailey, Ryan Rupert and junior defenceman Cody Donaghey. With 135 games of NHL experience but none since last season, Frattin is the only one in the group that might garner action with the Senators this season, Murray said.

Serious negotiations on the deal began over the weekend, according to the Senators GM.

"I hope it sends a message to our group that we're trying to win here," he said.