Bundesliga leading scorer Klaas-Jan Huntelaar insists it is important for Schalke to bolster their squad after qualifying for next season's Champions League.
The Royal Blues guaranteed third place in the Bundesliga as the Dutch ace netted twice and Raul was also on target in his last home appearance as they thumped Hertha Berlin 4-0 on Saturday.
The Spanish veteran, who turns 35 in June, looks set for a big-money move outside Europe at the end of the season after two years at the Veltins Arena.
And Huntelaar believes the club must replace the former Real Madrid man with another big-name player in order to compete with the likes of Bayern Munich and champions Borussia Dortmund.
"We are going to lose an important player in Raul," he told the club's official website.
"It's a big difference to have him at your club and it makes a difference to have him in your squad when you're travelling to an away game. He is a great player.
"Basically, I have complete trust in Heldt (Schalke general manager Horst Heldt) with the decisions in the summer.
"Schalke must sign some new star players but the fact that Jefferson Farfan has agreed a new contract is certainly a very good beginning and this is important for my future too."