One of the premier center-back pairings in MLS was split up on Friday, when Atlanta United officially announced the transfer of Leandro Gonzalez Pirez to Club Tijuana a few hours before LGP made his Xolos debut as the 2020 Clausura opened.

ATL promptly replaced one Argentine with another by signing Fernando Meza from Necaxa via Tijuana, but the partnership LGP shared with Miles Robinson will be tough to replicate.

While one high-end partnership has been lost, plenty remain throughout the league. To take stock of the top groupings around MLS, we’ve highlighted some of the tried-and-true ones that provide stability and routinely put out fires.

Often, these players serve as complementary pieces who bring out the best in each other. Their yin-and-yang relationships, based on past successes, should continue well into 2020.

LAFC – Eddie Segura, Walker Zimmerman

Walker Zimmerman was an MLS Best XI selection 2019 | USA Today Sports

So much of LAFC’s record-setting season was about the brilliance of Carlos Vela, so it’s easy to lose sight of how impactful Segura and Zimmerman were. They helped the Black & Gold post a league-low 37 goals against and stayed tuned in as the reigning Supporters’ Shield champions played on the front foot. Segura is now part of Colombia’s U-23 national team, while Zimmerman is a key piece for the US men’s national team.

Minnesota United – Michael Boxall, Ike Opara

A massive part of Minnesota United's turnaround in 2019 was landing Ike Opara | USA Today Sports

The Loons experienced a dramatic turnaround defensively in 2019, largely because Opara joined via trade from Sporting Kansas City. He ultimately became the 2019 MLS Defender of the Year, and signed a new contract in October after Minnesota went. So did Boxall, a New Zealand international who’s helped Minnesota go from historically bad to resolute at the back. The turnaround from a 70.5 goals-against average during their first two seasons to 43 in 2019 doesn't just happen overnight, with some credit also due for Vito Mannone, the 2019 Allstate MLS Goalkeeper of the Year.

New York City FC – Alexander Callens, Maxime Chanot

Alexander Callens, to date, has started 89 regular-season matches for NYCFC | USA Today Sports

Both international-caliber defenders, Callens (Peru) and Chanot (Luxembourg) provide a solid foundation for new NYCFC head coach Ronny Deila to build around. They're each 30 or younger, which means plenty of bright days lie ahead. Add in goalkeeper Sean Johnson to the mix, and you get a unit that allowed 42 goals last year, the league’s fourth-lowest total. One wild card here will be the return of James Sands from injury, since he was enjoying a breakout 2019 season as a third center back before suffering a broken collarbone in August.

New York Red Bulls – Aaron Long, Tim Parker

Tim Parker has started 129 regular-season games in MLS across his first five professional seasons | USA Today Sports

In terms of all-American partnerships, there’s likely none better in MLS than the one shared by Long and Parker. The former has become a USMNT staple under head coach Gregg Berhalter, and has been the subject of reported Premier League interest. Meanwhile, the latter has been an assured presence for the Red Bulls since joining via trade from Vancouver Whitecaps FC. Given New York’s pressing style, their athleticism and 1-on-1 defending skills tend to shine, and they could encounter an even greater spotlight with veteran goalkeeper Luis Robles now at Inter Miami CF.

Toronto FC – Omar Gonzalez, Chris Mavinga

Omar Gonzalez's arrival at Toronto FC coincided with their trip to 2019 MLS Cup | USA Today Sports

This partnership is still relatively young, since Gonzalez only joined Toronto from Pachuca last summer. Another factor at play is TFC have Laurent Ciman as a third option, so there’s depth at head coach Greg Vanney’s disposal. Yet, there’s promise in what an aerially-dominant veteran like Gonzalez could accomplish alongside Mavinga, a left-sided player who provides balance. With more games under their belt, all signs point to Gonzalez-Mavinga being among the best in MLS.

Also to consider…

Colorado Rapids – A question mark surrounds the Rapids next to Lalas Abubakar, but the Ghanaian enjoyed an impressive 2019 campaign before being acquired via via trade from Columbus. There’s also reason to believe that Abubakar and a to-be-determined center back could blossom under head coach Robin Fraser, a stellar defender during his playing days. Will it be Auston Trusty as he arrives from Philadelphia? What about Kortne Ford on his return from injury?

D.C. United – A 5-1 extra-time demolition at the hands of Toronto FC in the Audi 2019 MLS Cup Playoffs sours what was otherwise a strong 2019 season for the Black-and-Red's veteran center backs. Steven Birnbaum and Frederic Brillant each started at least 33 games last year as D.C. finished with 38 goals against, the second-lowest in MLS. Neither are particularly flashy, but they're ever-reliable.

Steven Birnbaum and Frederic Brillant challenge Zlatan Ibrahimovic for a header | USA Today Sports

FC Dallas – The buzz around Dallas often surrounds their young Homegrown stars, but it’s a pair of veterans providing lockdown defense at the back. Reto Ziegler and Matt Hedges provide a commanding presence and leadership, plus have proven dangerous on set pieces. Last year, they combined for six goals.

Philadelphia Union – The Union have a linchpin at the back in Jack Elliott, but it remains to be soon who pairs alongside the former SuperDraft fourth-rounder. Mark McKenzie could emerge as that partner after being called in for USMNT January camp, but he only started six matches last year. Veteran center back Aurelien Collin also started six matches in 2019, so it's premature to determine who forms the final duo.

Real Salt Lake – It’ll be interesting to see who emerges as the top pairing under head coach Freddy Juarez, since Justen Glad, Nedum Onuoha and Marcelo Silva all provide intriguing options. Onuoha was the most consistent presence with 27 starts in 2019, though a consistent stretch could do an eventual partnership wonders.

Justen Glad challenges Raul Ruidiaz for the ball | USA Today Sports

Seattle Sounders – The Sounders only have one center back under contract in Xavier Arreaga, though could easily enter the above conversation on firmer ground if a stalwart enters the frame. Yet, the retirement of Chad Marshall still looms large, Roman Torres signed with Inter Miami CF and Kim Kee-hee is currently not on the books.