Over the winter, Craig Breslow, chief baseball officer for the Boston Red Sox, swung trades for well-known veterans: starter Sonny Gray and first baseman Willson Contreras. In the midst of Boston’s improbable turnaround, however, an early-spring move for a less-heralded trio has arguably been just as impactful.That trade — a deal with the Milwaukee Brewers for infielders Caleb Durbin, Andruw Monasterio and Anthony Seigler — came a day before camp commenced. The Red Sox sent pitchers Kyle Harrison, Shane Drohan and infielder David Hamilton to the Brewers in the deal, which was a bit of a surprise amid Boston’s offseason-long quest for a third baseman.Durbin, coming off a strong rookie season, took on an immense task — filling the shoes of Rafael Devers and Alex Bregman. It was an impossibly tough assignment, especially with the Red Sox tied throughout the offseason to Houston All-Star infielder Isaac Paredes. Utilitymen Monasterio and Seigler appeared to be solid additions, but the early returns of the trade did not look good.Despite stabilizing the Red Sox defense at third, Durbin struggled mightily at the plate, hitting .163 with a .479 OPS through his first 48 games. Monasterio was in a platoon role and getting infrequent at-bats and Seigler was finding his footing at Triple A after missing all of spring training with an injury.Why the Red Sox resurgence is historicKen Rosenthal and Johnny SweetIn Milwaukee, Harrison dazzled in the first half, posting a 1.57 ERA through his first 11 starts.But the resurgence of Durbin, increased playing time for Monasterio and the call-up of Seigler have helped reinvigorate the Red Sox. The trio has been integral to the team’s rapid turnaround since the end of June. In one of the most dramatic wins of the Red Sox season, a 13-inning thriller on Aug. 7, all three played crucial roles, none bigger than Durbin’s walk-off single.“It’s very easy in the first couple months after a trade to take a small sample size, look and say, ‘Oh, that didn’t work out,’ interim manager Chad Tracy said. “Given time, you feel like you have a good idea of who the players are, and given time, you feel like they’re going to show up.”Caleb Durbin played a big role in Boston’s 13-inning win over the Chicago White Sox last week. (Charles Krupa / Associated Press)In mid-May, as Boston’s season spiraled, Tracy, who joined the Red Sox as interim manager after Alex Cora’s firing in late April, sat Durbin for a few games as a reset. Around that time, the 26-year-old began seeing a private hitting coach to augment the work he’d been doing with the Red Sox hitting staff. The extra work in the hours before heading to Fenway Park helped Durbin find his rhythm. The results came quickly.On May 26, Durbin was hitting .163/.241/238 with one home run. After Thursday, when he went 3-for-5 with a grand slam in Boston’s 7-0 win over the Blue Jays, he’s hit .309/.371/.517 with 11 homers since.