Beyond the game: Leveraging athlete celebrities for value creation in sportswear brands in the digital era

In the digital era, the strategic role of celebrity endorsements has evolved beyond traditional advertising to encompass real‐time, engagement‐driven marketing approaches. This study investigates the financial impact of athlete‐driven digital engagement on brand performance by analyzing the endorsement effects of globally renowned athletes across various sports. Using a novel Celebrities' Endorsement Index and an Extended Kalman Filter model, we quantify the influence of social media engagement metrics on stock market performance. Our findings reveal that high‐profile athlete endorsements significantly enhance brand equity, consumer trust, and investor sentiment, validating the halo effect and brand‐athlete congruence hypothesis. However, the analysis also uncovers a non‐linear relationship between digital engagement and stock performance, indicating diminishing marginal returns at high levels of endorsement saturation. These results bridge the gap between marketing and finance literature, demonstrating that real‐time engagement metrics can serve as leading indicators of firm valuation. Additionally, the study highlights the COVID‐19 pandemic's role in accelerating the shift toward digital‐first endorsement strategies, reinforcing the necessity for brands to integrate data‐driven celebrity marketing, AI‐powered analytics, and adaptive engagement models. Managerial implications emphasize the need for firms to optimize endorsement frequency, leverage real‐time engagement data, and align celebrity partnerships with corporate objectives.