Schalke manager Huub Stevens is slightly hesitant over the club's decision to offer Raul a new contract.
The Bundesliga outfit at the beginning of March confirmed a proposal had been emailed to the Spanish striker, who turns 35 in June, after months of discussions.
Raul, the top scorer in the history of the UEFA Champions League, is reported to want a new two-year contract, but Schalke are said to only be offering a 12-month deal.
And Stevens has even expressed caution over giving the former Real Madrid superstar, who moved to Germany in the summer of 2010, a one-year extension.
"You have to look at exactly what sort of performance he is producing, just like every other player," the Schalke boss told Bild.
"I don't know now how he will play in our remaining games and whether he can play so many games next season."
Ahead of Sunday's match against Hamburg, Stevens added: "Usually I judge a player by his development over a season.
"It is different with Raul, he is 34 years old and it is just a matter of him holding his level."