Some of the Twins' offseason improvement plans, notably a restructuring of the bullpen, haven't worked out as well as they hoped. But they seem to have made some rather startling progress in another targeted area: Infield defense.

The free-agent acquisition of shortstop Andrelton Simmons, the corresponding shift of Jorge Polanco to second base, and three solid weeks of a healthy Josh Donaldson at third base has drastically shored up the Twins' ability to turn ground balls into outs. In fact — while acknowledging that the season is only five weeks old, with less than 20 percent of the schedule played — the Twins are so far the best team in the American League at that useful skill.

Twins' opponents are batting just .192 when they hit the ball on the ground, easily the lowest average produced by any defense in the league. Not only is that one of the best rates in recent Twins' history ('s ground-ball records go back to 1988), it's a remarkable reversal for a team that has lived with subpar infield defense for years.

For 10 consecutive seasons, the Twins rated in the bottom half of the league in ground-ball defense, and opponents have racked up dozens, sometimes hundreds, of additional hits via ground balls in most years. A decade ago, for instance, the Twins' infield allowed a .268 batting average on ground balls, last in the then-14-team American League. Opponents piled up 491 hits on grounders. This year? They are on pace to total just 329.

"Adding Andrelton to the mix, when he's out there it does a lot of different things. It solidifies everything else on the infield," Twins manager Rocco Baldelli said. "Obviously we know J.D. is a very good third baseman, and Polo has done a nice job. He's still working over at second base and making adjustments."

Even Miguel Sano is improving at a position that's still new to him, Baldelli believes. The Twins' embrace of defensive shifts likely accounts for part of the team's improvement, too, but Donaldson and Simmons clearly give the Twins one of the most airtight left sides in the league.

"We have the guys to go out there and make a lot of plays in the infield," Baldelli said. "But we're not satisfied. We're going to continue to do everything we can to improve that group. But I do think our infield defense should be a strength of ours."

The last time that could be said was probably about two decades ago, when a foursome of Doug Mientkiewicz, Luis Rivas, Cristian Guzman and Corey Koskie kept opponents batting below .200 on ground balls for three consecutive seasons.

Opponent Batting Average on Ground Balls, 2021

.192 — Twins

.203 — Indians

.209 — Mariners

.212 — Blue Jays

.216 — White Sox

Twins' Opponent BA on Ground Balls (AL rank)

2021 — .192 (1st)

2020 — .240 (9th)

2019 — .244 (10th)

2018 — .248 (9th)

2017 — .259 (12th)

2016 — .261 (12th)

2015 — .255 (11th)

2014 — .261 (11th)

2013 — .246 (9th)

2012 — .252 (12th)

2011 — .268 (14th)