Banco Santander SA (SAN) shares are set for a rough start in pre-market trading on Wednesday, plummeting 5.01% as investors react to the Spanish bank's mixed first-quarter results. Despite meeting overall expectations, underwhelming performances in key markets have overshadowed the positives, leading to a significant sell-off.

While Santander's underlying trends for the first quarter aligned with consensus expectations, as noted by RBC Capital Markets analysts, the bank's performance across different regions varied significantly. The lender's operations in Spain and the United States exceeded estimates, demonstrating strength in these markets. However, these gains were offset by disappointing results from the UK and Brazil divisions, as well as the digital consumer bank, which fell short of investor expectations.

The pre-market plunge also reflects the high bar set by Santander's recent stock performance. With shares having surged 41% since the start of the year, investors were likely anticipating stronger results across all segments. The focus now turns to the bank's strategy moving forward, with analysts highlighting potential discussions around business unit disposals and the impact of global trade wars during the upcoming earnings call. As markets open, all eyes will be on Santander to see if it can recover from this early setback and reassure investors about its global growth prospects.