Bellingham underwent an operation to address a long-standing left shoulder issue that had been causing him discomfort since 2023. He had been playing through the pain for both his club and country.
"I want to be a bit optimistic and hope he can be back before October," Alonso said in a press conference. "He is starting to do some things with the group, and he has made a great effort in his recovery. He is feeling very well."
Bellingham finally decided to undergo surgery after the Club World Cup in the US, having reached his breaking point with the persistent injury. "I was sick of playing with the sling," he said back in June, having been frequently seen wearing shoulder strapping during matches.
The injury first flared up against Rayo Vallecano, forcing him to miss two games for both Real Madrid and England late in 2023.
A return for Bellingham would be a significant boost to the LaLiga leaders, who are currently top of the table with nine points alongside Athletic Bilbao.
Alonso is pleased with his squad's condition as they prepare for a demanding period that includes their Champions League opener against Olympique de Marseille.
"The most important thing is that everyone has come back healthy," Alonso said. "We haven't had any injury problems, and we're looking to maintain our perfect start in LaLiga and the Champions League."
Alonso is focused on preparing his team well for each match, setting short-term goals to help them navigate the challenging schedule ahead.
"We have to learn how to approach each match and focus on preparing well," he said. "During these international breaks, we have to set short-term goals to get us through April and May. We don't want to lose focus."