Lol, you have to read the part where Itachi and Kisame admit they would have lost against Jiraiya alone if they
BOTH fought him. And I know people will reply to this saying "Itachi didn't wanna capture naruto", yeah, well that doesn't mean he can just make up an excuse to Kisame to not fight Jiraiya. If Kisame knew Itachi was going to "rape" Jiraiya, then he would've said "never thought I'd have to go up against one of the legendary sannin, if we fight him, then the seven swordsman of the mist will have it's name dragged through the mud, but even though the Uchiha name could defeat the sannin"
INSTEAD OF HIS ACTUAL STATEMENT IN THE SERIES WRITTEN BY KISHIMOTO "never thought I'd have to go up against one of the legendary sannin, if
WE fight him, then
BOTH the Uchiha clan and the seven swordsman of the mist will have
THEIR names dragged through the mud".
Then Itachi responded with "true, but even the strongest of opponents...always has a weakness...". and that weakness he spoke of was Jiraiya's lust for women.
THAT was the biggest weakness Itachi had against Jiraiya.
By the way, people that say Orochimaru and Jiraiya being equals are seriously misinformed(saying that nicely)

. Orochimaru is probably Jiraiya's equal normally, but the second Jiraiya enters Sage mode, the gap in power is raised substantially. Evidence to back this up is when Shikaku said to Shikamaru to not interfere with Naruto and Pain's fight because their powers were on a whole other level from normal shinobi abilities. This basically means people who have achieved Sage mode talent are higher ranked shinobi.
But anyway, I know Itachi is insanely powerful, and Kisame has showed some very impressive abilities against Killer Bee and Gai, but Jiraiya STARTING in Sage mode with Orochimaru by his side, this fight will be way to uneven. Sage Jiraiya with Orochimaru and Orochimaru probably using IWR on unknown shinobi(most likely Kage-level) will be far too much for Itachi and Kisame.
Please Itachi fans, don't flame me. This is just my
opinion upon speculation from what I've read seen from the Naruto series altogether.