Santos has struggled to establish himself as Frankfurt’s first-choice goalkeeper after injuries and mistakes interrupted his progress.
The 23-year-old Brazilian was repeatedly given opportunities to take the position permanently, but Frankfurt signed Noah Atubolu from Freiburg shortly before the end of the summer transfer window.
Stein, who made 276 appearances for Frankfurt, believes a temporary move could give Santos the regular playing time and confidence he needs.
“He is a good lad and has huge potential. It would be a shame if he ended up sitting on the bench in Frankfurt. A loan is probably the best option,” Stein told Bild.
The former goalkeeper also believes Santos would benefit from moving somewhere he can play without the pressure of competing for his place after every mistake.
“I hope he can start somewhere new without any baggage. He needs the full confidence of the coach, and the feeling that he is allowed to make a mistake,” Stein said.
“He hasn’t had that opportunity in Frankfurt recently.”
Santos has shown his ability during his time at Eintracht, but injuries have repeatedly disrupted his progress.
Stein believes those setbacks, combined with the scrutiny surrounding mistakes, may have affected the Brazilian’s confidence.
“He has already made some great saves and definitely hasn’t forgotten how to be a goalkeeper because of his injuries. I think it is also a question of mentality,” he said.
“At Frankfurt, the discussion started again immediately after the first mistake. That naturally occupies a goalkeeper.”
Santos now faces competition from Atubolu for the starting role, with Stein suggesting a loan could provide the Brazilian with the consistent football required to regain momentum.