[WORLD] At first glance, two colleagues playing for rival soccer teams or sitting on opposing corporate boards might seem like a harmless coincidence. But what if those external rivalries quietly disrupt trust and cooperation back in the office? A recent study by Wharton’s Henning Piezunka provides data-backed evidence that these spillovers are real — and consequential. Using match data from elite soccer players, he finds that teammates who previously competed against each other show a marked decline in collaboration afterward. For leaders managing high-performing teams in business, the message is clear: external affiliations aren’t neutral. They can erode workplace cohesion in subtle but measurable ways.
Context: The Hidden Friction of External Loyalties
In many modern workplaces — especially in senior leadership and high-skill teams — people wear multiple hats. A CFO might serve on an outside board. A rising exec might campaign for a political cause. A designer might contribute to open-source projects. These roles often enrich careers, but they also create hidden channels of competition. As Piezunka observes, “conflicts they are having with each other do not actually take place within the team, but outside of the company.”
To study this effect, Piezunka and his co-authors analyzed professional soccer players who, while teammates on the same club, became adversaries on national teams during events like the FIFA World Cup. After such external competitions, these players passed the ball to one another 11% less during club matches — a statistically significant drop that reflects frayed collaboration.
The more strongly a player identified with the external group — in this case, the national team — the steeper the decline. This pattern holds implications for how much people prioritize in-group versus cross-group cooperation. In business terms: if your employee's loyalty to a rival external group intensifies, their willingness to share, support, or defer to teammates may deteriorate — even if everyone still sits in the same office.
Strategic Comparison: Not Just a Sports Phenomenon
Skeptics might argue that athletes are different. Professional sports are hyper-competitive, high-pressure environments. But the same behavioral dynamics play out in boardrooms and leadership teams.
Piezunka points to former Home Depot executives Carol Tomé and Marvin Ellison — who served on the boards of UPS and FedEx, respectively. Both logistics giants are direct competitors. While there's no public evidence of friction, the structural tension is obvious: can two executives truly collaborate without bias if they represent conflicting strategic interests outside the firm?
The analogy isn’t limited to Fortune 500 boards. As the lines between personal, professional, and political identities blur, workplace alliances are more easily strained. Take internal Slack debates over geopolitical conflicts, or colleagues discovering they supported opposing candidates in a local election. These aren’t hypothetical. They’re real fractures that can spill into project work, hiring decisions, or even how feedback is received.
Here’s the contrarian takeaway: it’s not diversity of thought that undermines collaboration — it’s unexamined dual loyalties. Many organizations celebrate external engagement as a proxy for leadership potential. But without cultural guardrails, those engagements can turn into liabilities.
Implications: Leaders Must Manage the Spillover
Companies can’t — and shouldn’t — ban external affiliations. Outside boards, side hustles, civic participation, and sporting passions all contribute to professional depth and personal growth. The real challenge is recognizing when these affiliations cross the line from enriching to corrosive.
There are three action points for leaders.
First, build a strong internal identity. Piezunka emphasizes the importance of team cohesion: “It’s very important that you strengthen the identity — that you are in it together when you are performing on behalf of your employer.” Shared rituals, common goals, and internal recognition systems help re-anchor employees to the firm.
Second, establish clear boundaries around external involvement. Basecamp famously banned political discussion on internal platforms to avoid social spillovers into work culture. While controversial, it reflected a growing need to preserve collaboration over ideological alignment. Managers must decide what kinds of outside activity are compatible with internal unity — and which aren’t.
Third, train for friction. Leaders should treat external competition as a predictable risk, not a rare exception. When a key team member joins an industry consortium that competes with a colleague’s external role, managers should intervene early. Framing the issue — not as a disciplinary matter, but as a collaboration risk — helps neutralize defensiveness.
Our Viewpoint
External rivalries aren’t just harmless background noise. They shape how trust, support, and collaboration play out inside the firm. As modern professionals stretch their influence across networks, affiliations, and industries, leaders must learn to read these tensions like a second language. It’s not about censoring people’s outside lives — it’s about designing a workplace culture resilient enough to contain their impact. Ignore the spillover at your peril. It’s already passing through.
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