It's been an up and down year for the Red Sox compared to last year's magical season. Remember that? The 2018 team won a record number of games, beat the Yankees in the playoffs, and won the World Series over the Los Angeles Dodgers thanks to magnificent performances by players like Mookie Betts, Xander Bogaerts and other members of the team’s young core of stars.

Alex Speier covers baseball for The Boston Globe. He also has a new book out called "Homegrown," about the Red Sox. Speier spoke with WGBH Radio’s Arun Rath about what it took to achieve last season’s success. This transcript has been edited for clarity.

Arun Rath: First, let's talk about the roots of this core that you write about in the book, the current Red Sox core. And to understand this, we have to go back to 2011?

Alex Speier: 2011 is when most of it came together. That was the last opportunity for a Major League Baseball team in the draft to commit, essentially, as many resources as it wanted to to accumulating young, amateur talent. So in that case, it was drawing players from college as well as high school. They took a lot of risks in that draft. They spent millions of dollars on players like Mookie Betts and Jackie Bradley Jr. The Red Sox recognized at an early point the opportunity presented by being able to spend big on amateur talents. The most efficient way to spend money in baseball is to find the proverbial diamond in the rough. That's a lot less expensive than spending big on giant diamonds, which is kind of what you could compare Major League Baseball free agency to, when you're spending $20 million, $30 million a year on elite talents. Instead, you're getting those guys for pennies on the dollar if you find them at an earlier point.

Rath: And what's appealing about this, as you lay it out, is it's not just spending the money, it's not developing individual athletes so much as developing the whole team. And I’m wondering if maybe you could talk a bit more about Mookie Betts, because he sort of illustrates that.

Speier: Yeah, it's really interesting because I think there's a lot of focus on players as individuals and on their individual growth, but simultaneously there's a complementary collective growth that has to occur in order for teams to become better.

In the case of Mookie Betts, he arrived in the Major Leagues on this kind of rocket ship through the minor leagues by 2014. He was only 21 years old. He found an environment in which he felt like an intruder, one in which he felt unwelcome, one in which he was getting a lot of negative feedback initially from the players who were surrounding him, and that hindered his performance to the point where he ended up getting sent back down to the minors — and was grateful to be sent back down to the minors. Imagine that. So over time, the Red Sox were able to align the environment and the culture surrounding the young stars that they had growing in a way that allowed them to perform better and to kind of realize that their ceilings, their peaks of their abilities, may exceed even what they knew.

In some respects, it was very intentional. The Red Sox invested a lot of thought into thinking, For the mental health of our players, what do we need to do? On top of that, some of it was, in a way, accidental. In 2015, some of their young players had struggled with their expectations. The Red Sox were on their way to a second straight last-place finish. That was a lot for them to carry. Their manager at the time, John Farrell, carried some of that attitude. Some of those expectations he internalized and externalized around those young players. He very sadly got diagnosed with cancer late in that season, in August of 2015, which led to successful treatment. He regained his health. But the interim manager who filled in for him during that time, Torey Lovullo, was someone who connected in a very special way with those young players. He's someone with a social psychology background from college, who had also managed for a number of years in the minor leagues, and really connected with players at that level of who they were becoming. He was able to convey baseball as a learning environment in a way that allowed a lot of those young players to reach new peaks in their careers.

Rath: So there was that magical season. Let's flash forward to now. It's not been quite as magical.

Speier: There’s been no magic, Arun.

Rath: I don’t want to be rude, but what happened?

Speier: It is a great reminder that cultural conditions and collective performance are fragile. This year, I think we're seeing a few different things at work. We're seeing the physical toll. It's been evident in the fact that the pitchers haven't been able to repeat their great performances of a year ago. So they're dealing with injuries, they're dealing with aging, and then that in turn, enters into the clubhouse, as do questions about their future. Because once players win, then they start asking, What's next? And in a lot of their cases, that means a question of their contractual futures, their futures with their teams.

So the Red Sox have had a lot of questions about who's going to become a free agent in the long term, who's going to resign and remain part of the fabric of Boston for years to come. So there have been different moving parts and different questions that have confronted them, and they haven't had the same answers this year that they did a year ago.