Much has changed since the last time the Ottawa Senators reached the second round of the NHL playoffs.

The 2012-13 squad succeeded as the "Pesky Sens" with a never-say-die attitude and repeated comeback and overtime wins. Four years later, the Senators' roster has seen significant turnover and brings higher expectations.

The only familiar faces in both starting lineups: the goaltender, top defence pairing and three forwards, one of whom barely played in 2012-13.

There's also a new coaching staff and management team.

Here's a look at what else has changed since the Sens' last Round 2 run.

Goaltending

Craig Anderson was the backbone of the 'Pesky Sens.' He remains a steady influence in net. (Francois Laplante/Freestyle Photography/Getty Images)

The more things change, the more they stay the same. Veteran goalie Craig Anderson has persevered this season as a finalist for the Bill Masterton Trophy while his wife Nicholle battles cancer.

This year's adversity is unlike anything Anderson has faced, but overcoming challenges has defined the 35-year-old's career.

In 2012-13, the Sens had two "goalies of the future" enter the crease in Ben Bishop and Robin Lehner. Anderson outlived both and remains a steady force between the pipes in Ottawa.

Defence

Erik Karlsson won the Norris Trophy in 2012 and 2015. He's up for another in 2017. (Minas Panagiotakis/Getty Images)

Erik Karlsson and Marc Methot have been a stabilizing force in the Senators zone for many years.

Karlsson, a two-time Norris Trophy winner, is nominated for a third nod this season, all while taking a more defensive posture and a larger leadership role as team captain. Of course, Daniel Alfredsson was the team's captain four years ago.

Besides Karlsson and Methot, the Sens' back end has a completely different look this year.

Dion Phaneuf replaces Sergei Gonchar. Cody Ceci replaces Chris Phillips. The third defence pairing has four new players fighting for two spots.

This year's defence has improved significantly in every important statistical category. Boucher has a part to play in that.

Forwards

Senators centre Kyle Turris led the team with six playoff goals in 2013. (Kirk Irwin/Getty Images)

This is where you will find the major on-ice changes. Kyle Turris and Zack Smith are the only two players remaining in Ottawa who played a full-time role four years ago.

Jean-Gabriel Pageau burst on the scene late in the 2012-13 season and scored four goals in the playoffs, including a memorable hat trick against the Montreal Canadiens in the first round.

The only other remaining forwards are Mark Stone and Chris Neil.

Stone only played one NHL playoff game in 2013 and spent the majority of that season with the team's American Hockey League affiliate in Binghamton, including three playoff games.

Neil is on the 2017 playoff roster, but at the moment it's unlikely he'll see a playoff game.

The Sens' forward line underwent major changes after the 2012-13 season. Alfredsson would sign with the Detroit Red Wings, while the Sens signed Clarke MacArthur as a free agent and acquired Bobby Ryan in a trade with the Anaheim Ducks.

Both MacArthur and Ryan have been big factors in the team's first-round success.

Coaching and management

Paul MacLean is now an assistant coach with the Anaheim Ducks where he's coaching former Senator Jakob Silfverberg.

In the team's second year under head coach Paul MacLean, Ottawa upset Montreal in the first round of the 2013 NHL playoffs.

The Senators would fall to the Pittsburgh Penguins in the second round but the team's surprising success saw MacLean named the 2012-13 NHL coach of the year.

That acknowledgement didn't carry weight for long, though, as MacLean was replaced by Dave Cameron in late 2014.

Cameron was let go last summer and Guy Boucher took over behind the bench, instilling his highly-touted defensive system.

Upstairs, Brian Murray stepped aside and Pierre Dorion was promoted to general manager. Alfredsson, forgiven by Sens fans for his brief foray to Detroit, traded his skates for a suit as a Senators adviser.

Daniel Alfredsson played his final season with the Senators in 2012-13. Now he's a member of the Sens' management team. (Fred Chartrand/The Canadian Press)

Here's a complete comparison of the two rosters, including all players who played at least one playoff game.

Goalies

Then: Anderson, Lehner.

Now: Anderson, Condon.

Defence

Then: Karlsson, Methot, Cowen, Gonchar, Phillips, Gryba, Benoit, Wiercioch.

Now: Karlsson, Methot, Phaneuf, Ceci, Wideman, Claesson, Harpur, Borowiecki.

Forwards

Then: Alfredsson, Turris, Spezza, Michalek, Smith, Greening, Pageau, Condra, Zibanejad, Silfverberg, Neil, Conacher, Stone, Latendresse, M. Kassian.

Now: Turris, Smith, Pageau, Stone, Brassard, Ryan, Hoffman, MacArthur, Stalberg, Burrows, Dzingel, Kelly, Pyatt, Wingels.