The San Diego Padres are one of the jewels of major league baseball: a small market team that is consistently competitive, supported by a loyal fan base, and whose beautiful downtown stadium generates millions of dollars for area businesses.

All of that feels in jeopardy amid a lawsuit filed by Sheel Kamal Seidler, who is the widow of the Padres’ late owner, Peter Seidler, who died November 14, 2023, at age 63. The lawsuit filed Monday in Texas claims two of Mr. Seidler’s brothers, Robert and Matt Seidler, breached their fiduciary duties as trustees of the Seidler Trust that controls the Padres. She alleges the brothers have “falsely cast themselves as Peter’s true heirs” and demands that she be placed in control of the franchise.

A messy legal battle lies ahead, potentially impacting the Padres on-the-field product, which has been very good, including reaching the playoffs last season. The uncertainty is already causing anxiety among fans like a San Diego native and long-time sports journalist, Lance Pugmire.

“As a typical fan we’re blindsided by it and want to know who’s on the right side of things,” Mr. Pugmire told The New York Sun. “Whoever is on the side of wanting the philosophy under Peter Seidler to be maintained that’s the right side. It’s hard to know what’s going on behind the scenes at this point.”

Peter Seidler, whose private equity firm purchased the Padres in 2012, was a beloved owner whose unwavering financial commitment to acquiring top talent elevated the team to prominence. He approved free agent contracts for players like Manny Machado and Xander Bogaerts and retained star players like Fernando Tatis Jr., Joe Musgrove, and Yu Darvish.

The Padres made the playoffs during the pandemic in 2020 and reached the National League Championship Series in 2022. They won 93 games last year and reached the post-season where they lost to the eventual World Series Champion Los Angeles Dodgers in the fifth game of the National League Division Series.

Meanwhile, Petco Park, which opened in 2004, has become a destination site. With the Chargers leaving for Los Angeles in 2017, the Padres are the city’s only major professional sports franchise. Lured by a good team and beautiful downtown ballpark, attendance for Padres home games ranked fourth in the majors last year with an average attendance of 41,117, trailing only the Dodgers, New York Yankees, and Philadelphia Phillies.

“The Padres mean everything to this city,” Mr. Pugmire said. “With the Chargers exodus to Los Angeles, all the major sporting attention has gone to the Padres. You’ve seen sellout crowds at basically every game which was unheard of before the Seidlers came in and dedicated the team to being top-shelf. They have Petco Park which is a great stadium and once they started investing in talent you’ve seen the results and they’ve been sensational.”

Peter Seidler was a two-time cancer survivor who died from an infection. After his death, the Padres payroll went from a team-record $257 million in 2023 to $166 million at the start of the 2024 season, a potential sign the franchise might be looking to curb salaries. Part of the lawsuit suggests “abandoning their all-pursuit of a World Series championship would have been a gut-punch to Peter.”

The lawsuit also claims that before his death, Peter Seidler expressed his desire for his wife to take over as the control person of the franchise. However, she later received a letter from Matt Seidler stating that she did not have the “experience skills and financial acumen” required to run a Major League team.  The lawsuit seeks to overturn the recent appointment of Peter’s oldest brother, John Seidler,  as the control person.

Seidler Trust issued a statement saying the lawsuit is “without merit” and John Seidler is the appropriate person to lead the franchise. “Peter had a clear estate plan,” the statement read. “The plan specifically named three of his nine siblings with whom he had worked closely for many decades, as successor trustees of his trust, and Peter himself prohibited Sheel from ever serving as trustee.”

In a post on X, a mother of three, Sheel Seidler, called the lawsuit “a last resort” that was filed “to protect my family and to continue to carry out Peter’s legacy” by being named the control person for the Padres. “I do not wish to litigate this matter in public, but rest assured I will do what it takes to protect my children,” she wrote.