The differences between last season’s downward-plunging Blue Jackets and the group that is competing for a spot in the Stanley Cup playoffs are vast enough to fill a college thesis.

Elite goaltending by Sergei Bobrovsky, who has “stolen” games the Blue Jackets otherwise would have lost.

Professional coaching by Todd Richards and his staff, who have defined roles and set a standard the players have achieved almost nightly.

A dressing room that no longer “hopes” to win, but expects to.

And there are several less-obvious reasons, including the Blue Jackets’ depth and competitiveness at center.

“Goaltending has probably always been the biggest position (of weakness) here,” Richards said. “The second position (of weakness) has been down the middle of the ice.”

But the Blue Jackets’ offseason acquisition of centers Artem Anisimov and Brandon Dubinsky from the New York Rangers, and the emergence of second-year pro Ryan Johansen has transformed the club’s forward lines.

Add Mark Letestu and Derek MacKenzie into the mix — they have bounced between wing and center all season — and the Blue Jackets now have a fairly formidable spine running through their forwards.

Anisimov is tied with Vinny Prospal for the team lead with 11 goals, and Letestu’s 23 points trail only Prospal’s 27.

Johansen, with linemates R.J. Umberger and Nick Foligno, has handled some of the toughest matchups against opponents’ No. 1 lines. He has had an “even” rating since March 1.

Tonight, that line could see a lot of time against the Ducks’ top line, centered by Ryan Getzlaf.

“Everybody wants better numbers (offensively), but (Johansen) has made huge strides this year compared to last year, just in his all-around game,” Richards said. “Playing against Datsyuk, the Sedins, Joe Thornton ... and playing well. He isn’t giving up a lot.”