If sasuke won without ms kakashi could definitely win because kakashi or sasuke is just a terrible match for deidara.
Sasuke did not win that fight, deidara commited suicide, there is a difference.
They were both at a stalemate, sasuke injured himself with chidori in order to disable the microscopic bombs, lost a wing and was low on chakra and literally on his knees from exhaustion and injury.
Deidara was in pretty much the same condition, it was a draw until deidara went bat shit crazy and BLEW HIMSELF up.
People also tend to forget that BOTH sasuke AND manda would have died in that explosion if SUIGETSU did not SAVE them.
Remember that it was Suigetsu who SUMMONED them away with that summoning scroll, sasuke did not defeat deidara, deidara killed himself, and sasuke dies too if suigetsu doesn't save him, this fight was a stalemate, a draw otherwise.
Plus don't go off on that sasuke without MS shit beat deidara, sasuke without EMS was almost, if not just as strong as MS sasuke. Please remember that sasuke had not only the cursed seal level 2 BUT he also had OROCHIMARU's powers too, he did ABSORB orochimaru afterall and had orochimaru's powers to help him in both his bttle against deidara and Itachi, Sasuke was already MILES ahead of Kakashi when he faced deidara, having already defeated orochimaru and gaining his powers before fighting deidara and going on to go toe to toe with Itachi after that, the same Itachi who outclassed Kakashi with only his 30% clone, prompting Kakashi to ask for Naruto's help to face him.
Plus deidara is way better than kakashi, remember that deidara went to fight Gaara with what sasori deemed as NOT ENOUGH clay, fought and captured the kazekage with insufficient clay,and lost an arm doing so.
Now Kakashi and Naruto meet up with a ONE ARMED deidara with EVEN LESS clay than he had against Gaara and they still almost lose.
Sure kakashi took his other arm, and he became armless, but this same armless, lacking in clay deidara kept up with Guy's team in TAIJUTSU, against a Taijutsu team without his arms and almost killed both Guy and Kakashi's team with his suicide clone. All done WITHOUT BOTH ARMS, WITH LIMITED CLAY and against like 9 PEOPLE on his OWN, and look at kakashi's condition afterwards, he was even worse off than deidara was because he needed to be caried awayafter absorbing the explosion because of mangyeko overuse, if Kakashi is alone deidara just goes and finishes him off because he was still good to go even then,
Don't underestimate deidara, he maybe bat shit crazy, but that holds no baring to his IQ and tactical proficiency, they guy is a great strategist and has insanely powerful jutsu's, at full power, kakashi stands no chance against him, face the facts. Kakashi is just a low S class and deidara is on the higher side of that rank, he will kill kakashi for sure in a one on one without any restrictions, with mid difficulty off coz thanks to kakashi's lightning element and kamui.