BOSTON — When Theo Epstein has made costly mistakes as general manager of the Boston Red Sox, they’ve tended to involve pitching.

The first time Epstein signed a young pitcher to a long-term, team-friendly contract, it was Bronson Arroyo — and, because the Red Sox appeared to have a surplus of pitching, he traded Arroyo to Cincinnati for Wily Mo Pena.

Epstein has never quite lived down that trade. He admits it was one of the most regrettable transactions of his Red Sox tenure. He since has learned just how valuable a commodity a young, talented, cost-controlled starting pitcher can be — not as an asset to be traded but as a franchise cornerstone.

He’s had just as rough a time at the other end of the financial spectrum.

The first time he invested more than $75 million in a player, it was for Daisuke Matsuzaka. The next time Epstein put more than $75 million into a player, it was for John Lackey. Neither pitcher yet has come close to justifying the cost.

That’s why Jon Lester and Clay Buchholz have a chance to be so important for the next four seasons.

“They’ve come from within and developed — and they’re still developing,” said Jason Varitek, who caught the no-hitters Buchholz and Lester threw early in their careers. “They both are. They’re still getting better, smarter, more efficient. It’s going to be fun to watch them over the years.”

Two years ago when Lester indicated that he was amenable to a team-friendly contract, Epstein jumped all over it. Lester will make $43 million and not hit the free-agent market until he’s 30 if the Red Sox pick up their option for 2014 — barely half of what the Tigers’ Justin Verlander will make during a similar length of time.

In the same way, when Buchholz indicated a willingness to sign a long-term deal — even at the steep negotiating cost of two team-option years — Epstein made sure the deal happened. Buchholz will make $57 million and not hit the open market until he’s 33 years old if the Red Sox pick up both of their team options.

Neither Lester nor Buchholz will be traded as Arroyo was. They’re not marketable assets whose low prices bring back greater return. They’re cornerstones of the Red Sox franchise.

Not only are they both capable of pitching 200 elite-level innings, but their presence atop the Red Sox rotation makes it far less likely Epstein will spend $80 million or $100 million on a free-agent starter who probably won’t end up being worth the money.

“Free-agent pitching is a tough way to go,” Epstein said after announcing the Buchholz extension. “We’ve dipped into those waters. If you can build an organization and not have to go into the free agent pitching market, that’s a good thing.

“It’s inevitable that you’ll have to go into it from time to time. But if you can develop homegrown pitching, control it, maybe control a couple of years of free agency a little bit, that’s a very valuable thing.”

The Red Sox insisted on getting two team options written into the contract. Had Buchholz not been amenable to that provision, the deal probably wouldn’t have happened.

It’s not as though Buchholz will be living close to the poverty line. He’ll make $13 million if the Red Sox pick up their option for 2016 and $13.5 million if they do so for 2017.

But his acceptance of that provision still represented a concession on his part. It pushes back his opportunity to sell his services to other bidders. A 31-year-old Buchholz — assuming he keeps pitching like a top-half-of-the-rotation starter — would command far more on the free-agent market than $26.5 million for two years.

“Obviously, we think very highly of Clay or we wouldn’t be doing this deal,” Epstein said. “With Clay being just 26 years old, the contract guarantees the salaries through the age of 30 — and having two club option years helps us. We expect Clay to be pitching very well at that point and can still be here in his age-31, age-32 seasons. It just gives the club a little more flexibility in exchange for the security that we’re providing through the deal.”

Matsuzaka is under contract for the 2012 season at a cost of $10 million. Both Josh Beckett and Lackey are under contract through 2014 at a combined cost of $31 million per season. Even the big-market Red Sox can’t afford to devote $75 million to their starting rotation — and that’s what it would take if they pursued a free agent such as Cole Hamels, Francisco Liriano or Jered Weaver after the 2012 season.

Instead, the Red Sox expect to get similar production at a fraction of the cost out of Buchholz and Lester.

“We all know the cost of free-agent pitching,” Epstein said. “The longer we can put off that decision, from the club’s perspective, the better. While it’s a lot of money, compared to what it costs to bring in a free-agent contract on a long-term contract, it’s actually not that much money. The risk-reward, we felt, were certainly worth it from our perspective. Without the option years that give us some flexibility, we would have been less comfortable from the club’s standpoint.”

Augusta and Waterville news

Get news and events from your towns in your inbox every Friday.

  • This field is for validation purposes and should be left unchanged.