Which teams most improved in the summer transfer window?

With the MLS Secondary Transfer Window officially in the rearview mirror as of Wednesday night, which teams did the best job of bettering themselves in the market? 

I’m here to answer that question with five clubs that truly boosted their outlook with savvy summer business.

Notable incomings: Jack Harrison, Matt Turner, Dániel Gazdag

Sure, Matt Turner was already a New England Revolution player when the year began. But with his loan from Lyon expiring this summer, the Revs’ front office still had to roll up their sleeves to secure a deal that would keep their star goalkeeper around for a while longer. They managed exactly that, keeping the USMNTer on loan through potentially the end of 2027 with a purchase option. Turner, who leads the league in goals prevented (according to FotMob), is every bit a building block for New England.

Plus, the new deal moved Turner off of his Designated Player tag, giving the Revolution additional roster flexibility.

With Jack Harrison joining the fray as a DP from Leeds United, New England have put that roster spot to good use. Harrison has brought a lightning bolt’s worth of energy to Marko Mitrović’s attack courtesy of his dynamic dribbling, clever vision and varied passing range.

With Harrison, Peyton Miller, Carles Gil and the arrival of former Philadelphia Union star Dániel Gazdag, the Revolution’s attacking midfield band is suddenly one of MLS’s most well-rounded.

Add some fun young additions to those key pieces, and New England are undoubtedly better off than before the summer.

Notable incomings: Breel Embolo, Mauricio Amaro, Paulo Díaz, Júnior Alonso

It hasn’t been smooth sailing for Atlanta United throughout 2026. In fact, the seas have been relatively choppy. But even as the Five Stripes try to climb the Eastern Conference standings in what was always destined to be a multi-year rebuilding process, they've done an admirable job of reshaping the roster this summer.

The biggest arrival, of course, is Breel Embolo. The Swiss international striker joined from Stade Rennais for reportedly around an $18 million transfer fee, fresh off an impressive World Cup and a Ligue 1 season where he proved a consistent goal threat. With Emmanuel Latte Lath off to Bundesliga side Union Berlin on loan (another good piece of business from Atlanta), the runway is clear for this to be Embolo’s team.

Elsewhere, Mauricio Amaro is a highly rated young No. 6 who joined on a U22 Initiative deal and is expected to be a key piece moving forward. Then there's Díaz and Alonso, who help solidify the back line and bring boatloads of experience from South America.

This summer has brought much-needed progress for Atlanta United.

Notable incomings: Rafael Navarro, Carlo Holse, Damion Downs, Alexandru Mățan

St. Louis, perhaps more than any other MLS club, had an adventurous summer transfer window. With Marcel Hartel heading back to Germany and Eduard Löwen being traded to the San Jose Earthquakes, there were big shoes to fill.

But with their suite of major additions, it certainly looks like St. Louis filled those shoes – and then some. 

The headliner is, of course, Rafael Navarro. Signed for a $12 million cash trade from the Colorado Rapids, the Brazilian striker will be expected to lead CITY's new era. A mobile, well-rounded No. 9, Navarro could blossom into one of MLS’s most prized players.

Elsewhere, to help cover for Hartel’s exit, St. Louis added new Designated Player Carlo Holse from the Turkish top flight. The 27-year-old Danish international, capable of playing a host of positions, has already scored his first MLS goal since joining the club and looks right at home.

Elsewhere, USMNT striker Damion Downs, signed on loan from Southampton, looks set to provide a more vertical dimension to Yoann Damet’s side. And they've brought Alexandru Mățan back to MLS, a solid addition in the attacking line.

With more firepower and continued on-field success, St. Louis look primed to continue their rise.

Notable incomings: Robert Lewandowski, Noah Allen, Anzor Mekvabishvili

One of the league’s true heavy-hitting clubs, the Fire signed a superstar this summer: Polish legend Robert Lewandowski. After an astonishing amount of success at Borussia Dortmund, Bayern Munich and FC Barcelona, Lewandowski moved across the Atlantic to become Chicago’s starting No. 9.

While then-starter Hugo Cuypers was transferred out not long after Lewandowski’s arrival, the veteran brings an impressively refined skill set to the table. There’s a reason why he scored more than 300 goals in the Bundesliga before averaging more than 20 goals across his four-year spell in Spain. Still, Lewandowski is more than just a scorer. His on-ball play adds a different dimension to Gregg Berhalter’s attack and has already helped make Chicago’s wingers more dangerous.

Even outside of Lewandowski’s star power up front, the savvy addition of Noah Allen from Inter Miami is also a standout move. He can provide the Fire with valuable minutes as either a left center back or a left back. It's a needed boost as Mbekezeli Mbokazi recovers from a long-term injury.

Add in valuable depth that arrived from Europe to bolster the squad (see Georgian midfielder Anzor Mekvabishvili and Norwegian defender Andreas Hanche-Olsen), and Chicago have raised both their ceiling and floor.

Notable incomings: Casemiro, Fricio Caicedo, Matías Galarza, Riquelme Fillipi

One of the greatest midfielders of his generation now plays for Inter Miami. 

Casemiro, who plied his trade for Real Madrid and Manchester United before signing with Miami after Brazil’s 2026 World Cup campaign, has brought an immediate boost to his new team. Dangerous in the tackle, yes, but even more dangerous on the ball in possession, Casemiro’s arrival has bolstered Inter Miami’s attacking play. With his pinpoint passing and clever ball-carrying, the Brazilian has made life even more difficult for opponents trying to slow down the Herons.

It’s not just Casemiro who’s shown transformative ability for Inter Miami since joining this summer. Something similar could be said of rising Ecuador international defender Fricio Caicedo. Just 18, Caicedo checks just about every box you’d want a center back to check. His size, range and possession ability jump off the screen.

With even more quality options added in midfield (Matías Galarza) and the attack (Riquelme Fillipi), Inter Miami look set for another late-season run – one that could end in a second-straight MLS Cup presented by Audi title.