Merida is in the middle of new contract talks with the Gunners.
"I think it's massive for us that he's signing a new deal because I believe he's an outstanding player," said Wenger to arsenal.com.
"He has technical quality and he knows where to stand on the pitch. You can't give that to people. He has that quality of the pass in the final third and he sees things. And he's aggressive. He's a man on the football pitch and despite his size he's ready for a fight.
"He's in the first-team squad and I believe we prepare and we make room for the players we sign on a longer term."
If Merida had opted to leave Arsenal he would have been free to speak to other clubs from January 1 and Wenger believes that interested parties have already attempted to destabilise the Spaniard. The manager doesn't mind clubs taking an interest in his players - but he does mind them breaching the rules.
"I can't say I'm annoyed by other clubs going after our players because we do it as well. But we do it legally," he said.
"The difference is that we do not do what is not allowed by the law. We try to get the best players everywhere when it is allowed by the rules.
"For example in this case Fran Merida is at the end of his contract at the end of the season, but we know as well that means he could be contacted on January 1, 2010. We are not naïve enough to believe that he will get the first phonecall at midnight on January 1."