Saul arrived with high expectations on loan from Atletico Madrid on transfer deadline day, but the midfielder has struggled to make an impact during his early days at Stamford Bridge.
The 26-year-old endured a nightmare debut against Aston Villa before starting against Dean Smith's side in the EFL Cup, and Alonso has backed his fellow Spaniard to shine for the club.
Speaking to Cadena SER, Alonso said: "Well, he's a newcomer. He's in the adaptation phase, but he's a great player and he's going to be very good for us."
Saul has been an unused substitute in Chelsea's last three Premier League games after his debut versus Villa, during which he lasted just 45 minutes before being hooked by Thomas Tuchel.
The Spaniard's existing deal at Atletico is due to expire in 2026, and Chelsea possess a £30m option to purchase him permanently at the end of the campaign. body check tags ::