Shares of Banco Santander SA (SAN) tumbled 5.01% in pre-market trading on Wednesday, despite the Spanish bank's overall first-quarter results meeting consensus expectations. The sharp decline appears to be driven by disappointing performances in key markets and divisions, overshadowing positive results in other areas.

While Santander's operations in Spain and the United States exceeded estimates, investors seem to be focusing on the underperformance in the United Kingdom, Brazil, and the bank's digital consumer division. Citi analysts noted that these weaker results "might not feel enthusiastic" to investors, especially given the stock's recent outperformance, having gained 41% since the start of the year.

RBC Capital Markets analysts Benjamin Toms and Pablo de la Torre Cuevas highlighted that the focus of today's earnings call will likely be on recent news about business unit disposals and the impact of global trade wars. They also pointed out that while the bank's corporate and investment banking division shows a good mix of high growth and profitability with effective cost control, its recent expansion into the U.S. market may have been poorly timed. As Santander navigates these challenges, investors will be closely watching for any strategic shifts or improvements in underperforming segments.