Clay Buchholz put it simply.
"We talk to John a lot, and I'm around him every day, but on the pitching side of things, [Juan Nieves] is the guy everybody goes to."
Nieves is the man who sits in the room behind the corner office, just past the clubhouse. He's the one who showed up to Fenway Park early Sunday morning to study more tape of a Twins offense the Red Sox won't face for more than a week. He's also the one now assigned with Farrell's old job, the pitching coach.
Farrell likes to delegate responsibility. He doesn't step on the toes of his other coaches. He puts faith in them.
In return, Nieves has helped turn around a pitching staff that ranked 27th in the Majors last season with a 4.70 ERA. Through Sunday, the Red Sox ranked seventh with a 3.39 ERA, as they owned the best record in the Majors at 18-7.
"One of the biggest things I've always said about this team is they've seen death in their own eyes," Nieves said. "It's been tough the last year and a half, but the way these guys come together, and they stick together, and they fight together, they work together -- it's amazing. You would think after going through tough times the bitterness would be very hard."
About 20 minutes had passed in the first official workout of Spring Training and Buchholz had injured his right hamstring while trying to cover first base during a drill.
Newspaper headlines brought a moment of fear back to Red Sox fans. Buchholz, though, felt little of that.
"When I was out for that couple weeks, [Nieves] would just send me little texts, like, 'Hey, just thinking about you. Hope everything is going well,'" Buchholz said. "Whatever we have on the schedule, if we're throwing a bullpen [session] the night before, he'll text me, 'Hey, just want to let you know it's a good step in the right direction. Can't wait to get to the field and get you off the mound a little bit.'
"He just makes you feel good about the process, and right there is probably the biggest key for me."
Buchholz hardly missed a beat in Spring Training, while the confidence Nieves has helped him recapture has carried over to the season. Buchholz is off to a 5-0 start with a 1.19 ERA after posting a 4.56 ERA in 2012.
"He's one of the best, if not the best, coaches I've been around," Buchholz said. "With everybody, not just me. He's a real positive type of person. There's always something positive to take, even situations that it's hard to take good thing from, he finds a way to get positive information and make you feel good about different things. You don't get that with everybody.
"It's a tough job to do, especially when you have guys that have been in the big leagues for a little bit, to try to make them feel good about something that maybe was a failure."
Jon Lester doesn't seem to lose his temper with umpires as often as he used to, and he went four starts this season without having a problem.
Until his last outing, Wednesday against the A's, when he was finally ignited again. Lester walked two in the first inning and at least one batter in five of the six innings he pitched in. He was screaming from the mound and punching his glove as he walked off.
"I mean, once or twice, it's easy [to forget about]," Lester said. "After a while, it's frustrating.
"I'm an emotional person, always have been, and it's tough to control that sometimes."
For a pitcher with as much talent as Lester, his 4.82 ERA in 2012 was a surprise to many. A lot of it has been mental, but Nieves has helped with that.
"He's a competitor out there almost to the point where he gets mad at himself, and that's where Juan and John come in," Buchholz said.
"When [Lester] comes in the dugout, you can see his wheels turning, but [Farrell and Nieves] are able to go talk to him, just go, 'Hey, settle down and make a pitch. That's what you're going to do. You're going to get the outs and your stuff is going to play.'"
The six-walk outing was Lester's worst of the year, and yet he still finished 5 2/3 innings, allowed just three runs and picked up his fourth win. The Red Sox have won every game he's started.
With Nieves around, calmness often overrides rage for Boston's No. 1 starter.
"Juan is a very positive guy, so I think that helps," Lester said. "No matter what the situation is, he's going to find the positive out of it. That helps clear your mind so you can go back to doing the job you have to do."
Nieves credits esteemed White Sox pitching coach Don Cooper for giving him so much responsibility as the team's bullpen coach from 2008-12. The positive attitude and friendly smile, those are Nieves' trademarks.
"If guys have a bad game, it's OK. They're human," Nieves said. "I always say, if Pedro Martinez lost a game, anybody can lose a game."
Nieves doesn't ask for perfection. He asks that his pitchers do their best at what they can control: throwing strikes, fielding their positions and being prepared.
Even veteran starters are feeling the difference.
Behind Nieves, Lester, Ryan Dempster and John Lackey are enjoying success thanks in part to getting ahead of batters. All three of them are throwing first-pitch strikes more often than any other time in their careers.
Lester, Lackey and Buchholz, who have struggled at times with men on base, have set career highs this season while stranding 81, 86, and 90 percent of their baserunners, respectively.
The game plan starts early. Nieves begins watching video of opposing teams' at-bats weeks in advance. He showed up before most on Sunday morning simply to watch video of two players, Brett Lawrie and Munenori Kawasaki, who weren't on the Blue Jays' roster the first time the Red Sox faced them earlier this month.
Then Nieves sat down with Lackey, Sunday's starter, and catcher Jarrod Saltalamacchia to discuss a game plan for Astros hitters. After three games in the series, Houston hadn't had much success offensively, but Nieves wanted to be sure hitters weren't picking up patterns from Red Sox pitchers.
After the meeting, Nieves administered pitchers' fielding practice, typically something reserved for Spring Training. He said it wasn't punishment, but with the sun shining and the temperature in the 60s, it presented a good opportunity.
Lackey then tossed six innings of one-run ball to win Sunday's game and complete the Red Sox's four-game sweep against the Astros in which Boston pitchers allowed just 10 runs.
Nearly an hour after the final pitch, Nieves was still in full uniform, chatting with Farrell in the corner office.
He had yet to take a shower.