Jimenez picked up a yellow card in the first half for a foul on Whites midfielder Robin Koch and then appeared to catch Meslier late on 50 minutes as the pair raced towards a loose ball.
Referee Kevin Friend produced a second yellow and sent off the Wolves striker, with his side 2-0 to the good. Leeds, who lost Meslier to a hip contusion from his clash with Jimenez, then roared back to win 3-2 late on thanks to goals from Jack Harrison, Rodrigo and Luke Ayling.
Wolves boss Bruno Lage was furious with Friends' decision to send off Jimenez and both he and his opposite number Jesse Marsch agreed that it changed the game completely.
Speaking on Sky Sports' Ref Watch, Gallagher sympathised with Lage's forward and disagreed with the decision. He believes Friend was given poor advice.
"I think it's very unlucky," he said.
"I think the assistant gives it, he has a sideways view and sees him collide late, thinks he's gone in late and fouled him and told the referee to give him a second yellow card, so he's sent off.
"The irony of it is, if the VAR can't get involved, it's all or nothing, because he's already on a yellow and gets a second. He's desperately unlucky to be sent off, desperately unlucky to be serving a ban and even more that he can't appeal a second yellow card. He didn't have a particularly good night."
Gallagher added that had a red card been shown, hypothetically, instead of a second yellow, VAR would undoubtedly have overturned it.
"I think it's a collision, two players going for the ball, the goalkeeper's got to go for the ball that's his job, the forward has to go for the ball he's trying to score a goal. I think the two players have collided, it's inevitable, these things happen on football fields," he said.
"Looking at the pictures now he's really unlucky for a number of reasons."