MESA, Ariz. — For years, Chris Bosio was credited as part of the reason for the Cubs’ recent string of pitching success. He helped turn Jake Arrieta into a Cy Young winner and oversaw pitching staffs that led the Cubs to three consecutive NLCS appearances and that curse-smashing World Series win in 2016.

But now it’s 2018, and Bosio is out. Jim Hickey is in.

The Cubs’ new pitching coach arrives with high expectations and has been tasked with shepherding a group of arms that saw a few too many bumps in the road last season. Jon Lester had his worst season in a long time, Jose Quintana’s numbers weren’t as good as they had been during his time with the White Sox, Tyler Chatwood led the National League in losses last season, and Yu Darvish got roughed up in a pair of World Series starts. And that’s before even mentioning the bullpen.

Still, even with all that said, the Cubs look to have, on paper, one of the best starting rotations in the game. And the upgrades in the bullpen have tempered some of the rage over the relief corps’ repeated postseason implosions. Theo Epstein’s front office had a mission this offseason to improve the pitching staff, and Hickey is a very large part of trying to accomplish that mission.

“What really was the slam dunk in my decision to come to Chicago or at least the finishing touches on it was getting to meet Theo, getting to meet Jed (Hoyer), going physically to Chicago, go to the offices there, seeing the physical building, meeting the people inside, just getting that vibe. Everybody was on the same page, and that page was winning,” Hickey said in an interview with NBC Sports Chicago. “And also built not just to win here for two or three years but for a sustained period of time, and that was what was very, very attractive.”

Hickey’s ties to the Cubs are obvious. He worked as Joe Maddon’s pitching coach in Tampa Bay for eight seasons before Maddon left to take over managing duties on the North Side. The two coached some phenomenal pitchers with the Rays, guys like James Shields, David Price, Scott Kazmir and Chris Archer and won an American League pennant in 2008. Prior to that, Hickey coached for the Houston Astros and oversaw a staff that included Roger Clemens, Andy Pettitte and Roy Oswalt en route to the 2005 World Series.

How does the Cubs’ rotation of Lester, Darvish, Kyle Hendricks, Quintana and Chatwood compare to those great rotations from Hickey’s past?

“That’s a really tough question. But I think one through five, it may be as deep as any staff that I’ve had,” he said. “Really tough to say. I’ll give you a better idea after the season’s over, but one through five, it’s really, really good. Had some very, very good staffs, obviously, in years past. But these five guys, we talk about it all the time, the starters pitching innings and not falling into this pattern of starters being used less and less and the bullpen being used more and more.

“If you were to give me a staff of five guys, or give anybody a staff of five guys, that threw between 185 and 200 innings, you would probably have a championship-caliber club. And that’s what my expectations are out of this staff, and I think they will be a championship-caliber club.”

Hickey’s toughest task, though, likely won’t be working with all those veteran starters but instead working with a bullpen that struggled under the bright lights of the postseason last October. While Cubs relievers had the sixth-lowest ERA in baseball during the regular season (3.80), the playoffs were a different story, with the bullpen rocked to the tune of a 6.21 ERA. Cubs relievers walked a postseason-high 27 batters while striking out only 35 in 37.2 innings.

The front office tried to fix that strike-throwing problem by bringing in new closer Brandon Morrow, who shone with the Los Angeles Dodgers last season, and Steve Cishek, who has closing experience from his time with the Miami Marlins and Seattle Mariners, plus he worked with Hickey last season in Tampa Bay.

But Hickey is the bigger key to fixing that problem, and it’s one of his biggest objectives to not just bring the walks down but make the Cubs one of the best staffs in baseball when it comes to issuing free passes.

“I really think that walks, especially out of the bullpen, are a little bit more of a mindset than they are anything physically or mechanically wrong,” he said. “You come into a situation where maybe you give up a base hit and maybe it changes the game, so you’re a little bit reluctant to throw the ball over the plate.

“So I think it’s more of a mindset, and once the group gets the mindset of ‘attack, attack, attack,’ it’ll be contagious. And I think it is contagious. I think last year it was probably contagious in that there was more walks than you would like, and I think as you turn the corner and head the other direction, that would be contagious, as well.

“I have very few outcome goals in a season. I don’t sit there and say, ‘I want to lead the league in earned-run average’ or ‘I want to lead the league in strikeouts.’ … But that one thing, that one outcome goal that I always have for a staff is to have the least amount of walks in the league. And I think at the end of the day, especially with the talent that’s out there, if that is the case, it’s going to be an extremely successful season.”