What Jake Diekman and Matt Strahm, the Red Sox’ two new lefty relievers, bring to the bullpen

Jake Diekman's three-quarter arm slot can be difficult for hitters to deal with.Louis DeLuca/Associated Press

The Red Sox have added depth to their bullpen, acquiring lefthanders Jake Diekman and Matt Strahm. Diekman, 35, most recently played 2½ seasons for the Athletics. Strahm, 30, was a member of the Padres for the last four years.

Diekman’s deal is for two years and $8 million, with a $4 million team option for 2024 or a $1 million buyout; he will make $3.5 million in both 2022 and 2023. Strahm’s deal is for one year and $3 million.

Each comes with the hope that he can bolster the Red Sox bullpen. Here’s a breakdown of both:

▪ Diekman leans heavily on his four-seam fastball/slider combination. The average velocity on his fastball was 95.3 miles per hour last year, but with his wiry 6-foot-4-inch frame and three-quarter arm slot, it can smother the hitter or be a difficult pitch to time.

If Diekman’s wipeout slider is working — a pitch that held hitters to just a .121 batting average last season — he can be a dominant reliever.

Take the 2020 season, for instance. Diekman was one of the best relievers in baseball, carrying a 0.42 ERA in 21⅓ innings. He flashed 13.1 strikeouts per nine innings, the highest mark of his career.

“He has big stuff,” an American League executive said. “He misses bats and will take the [ball]. But his command fluctuates.”

Inconsistency is common for relievers. And over a 162-game season, command fluctuation has more wiggle room to reach the surface. The 2020 season was shortened because of COVID-19, and while Diekman’s numbers were impressive — especially if you consider all the peculiar circumstances — the sample size wasn’t big enough to make a fair assessment.

In 2020, Jake Diekman was one of the best relievers in baseball, carrying a 0.42 ERA in 21⅓ innings.Darron Cummings/Associated Press

The 2021 season, however, was.

Oakland’s plan heading into that season was to use a closer by committee. On some days, Lou Trivino would get the role. On other occasions, it would be Diekman. But Trivino took over as Diekman blew as many games (7) as he would save.

Diekman was placed in the setup role, but the A’s decided to trade for Andrew Chafin, another lefty, because Diekman became unreliable. In the end, Diekman was behind Trivino, Chafin, and Yusmeiro Petit.

Following a splendid August in which he posted a 1.64 ERA, Diekman sputtered in September. He yielded an 8.18 ERA that month, allowing a whopping 10 earned runs in 11 innings.

Nevertheless, at the season’s completion, Diekman held a respectable 3.86 ERA, striking out 12.3 batters per nine innings (83 in 60⅔ innings). That is likely in line with who Diekman is. He has a career ERA of 3.73 and averages 11.5 strikeouts over nine.

“As a reliever, some years are going to look better than others, but he’s been very consistent with the three-batter minimum,” said Padres manager Bob Melvin, who managed Diekman with the A’s the three previous seasons. “And every lefty I talk to [that has faced him] says it’s a real difficult ball to pick up.

“He’s definitely an effective lefty and he’s been doing it for quite a while.”

Diekman isn’t a top-tier reliever, but he certainly can be a very good one and give the Red Sox flexibility. He has had success against both lefties and righties; righties batted .200 against him last year while lefties hit .229. Manager Alex Cora should feel comfortable employing him in different scenarios, not just lefty-on-lefty matchups.

▪ Strahm dealt with a right knee injury much of the last two seasons. In September 2020, he was placed on the injured list with inflammation. In April 2021, the knee required patellar repair. He was activated in August, but by September the Padres decided to shut him down. He finished with just 6⅔ innings of work for the season.

Matt Strahm has a career ERA of 3.81.Sue Ogrocki/Associated Press

Strahm doesn’t overwhelm hitters with velocity; he is more of a finesse pitcher. His four-seamer averages around 93 m.p.h. Like Diekman, he plays the fastball off the slider.

His numbers show him as somewhat of a reverse split-type pitcher. Righties have a career .229 batting average and .699 OPS against Strahm, while lefties are at .253 with a .732 OPS.

Strahm’s best season came in 2018 when he put together a 2.05 ERA and 0.978 WHIP in 61⅓ innings.

The additions of Diekman and Strahm were the Sox’ first attempt this offseason at trying to bolster their bullpen, one that stood in the middle of the pack last year but faltered in the playoffs, registering a 5.23 ERA. It’s a long time until October rolls back around, but the moves certainly detail what is at the top of the team’s to-do list.