By Bruce Levine-

(CBS) — The evolving Chicago Cubs bullpen has been a pleasant surprise for a team that has compiled the best record in the National League the last 31 days.

Power arms picked up in trades and developed through the minor league system have kept the team close late in games this season.

A well laid out plan by new manager Rick Renteria and the pitching gurus led by Chris Bosio have worked wonders with a group of unproven power arms. Leadership from veterans Carlos Villanueva and Brian Schlitter have helped the inexperienced young bullpen core. All of the above have made the difference in many of the Cubs’ victories this season.

Bosio, who was given a two-year extension that includes an option for 2016, has his concerns on the long range protection and development of the big bullpen arms.

“Ideally you want your starters to go seven innings. You don’t want to tax your young guys,” Bosio related to me on Sunday. “Somewhere though there have to be guys picking up the slack, that is why we are carrying eight guys in the bullpen. It is something we monitor every day with our charting of innings, appearances and times they get up to warm up during games.”

The past couple of seasons pitchers like James Russell and Shawn Camp threw an uncomfortable amount of innings that had an impact on their viability and in the case of Camp his career. Russell made 151 appearances combined in 2012-13.That type of wear and tear has been controlled this season. The front office has supplied a second left hand pitcher, Wesley Wright, on the club that the Cubs did not have in the pen last year.

“We have one of the healthier staffs in baseball,” Bosio said. “That is something we are proud of. We try not to pitch guys three times in a row. If we do, we monitor it so that one of the pitch counts the previous day has to be lower. We also stay on top of their shoulder programs with our medical and training staff as a part of the plan.”

When the Cubs starters do not pitch the proper amount of innings in back to back games, like Friday and Saturday where Edwin Jackson and Travis Wood combined to throw eight and two-thirds innings, the situation can get a little rough for the coaching staff and the plan of attack.

“We do have to mix and match when that happens.” said Renteria. “We know what we have, we know what they can do. The reality is if you use the bullpen early, you may not have the best match ups. However, we do have really good game plans and they are major league pitchers. They should be able to navigate through these situations even when the match ups are not that good.”

The Cubs bullpen has a 3.05 ERA, the fourth lowest in the National League this season. The pen had a 4.14 ERA through 72 games in 2013. Only Justin Grimm and Schlitter, are on pace for 70 plus appearances.

Watch & Listen LIVE