He made 12 appearances this season but has not played since a 2-2 draw with Leicester City on Oct. 17.
Shorn of Rodriguez, Southampton's options up front are limited and Koeman said striker Sadio Mane would not be sold despite speculation linking him with a move to Chelsea or Manchester United in January.
Mane joined Southampton from Red Bull Salzburg in September last year and has six goals this campaign.
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"Rumours aren't important. We will sell nobody," Koeman told reporters. "You can ask again about Sadio, Man United, Chelsea, but we will sell nobody in January."
Koeman added that Mane had yet to reach his full potential but was working to achieve that at Southampton.
"Because the player is developing himself, with all the help from the technical staff and the rest of the players. They are showing qualities, and then of course big teams are interested," he said.
"It's a normal progress of players who are developing themselves.
"In my opinion it's not about money, it's about ambition of players and people," he added.
Southampton, who are eighth in the Premier League and saw a six-game unbeaten run end at Stoke last weekend, travel to face third-placed Manchester City on Saturday.
(Reporting by Simon Jennings in Bengaluru; Editing by Peter Rutherford)
