Gary Warren's first half header at McDiarmid Park sealed the three points but Hughes said: "Can we catch Aberdeen?
"I don't know, it depends what we do, it depends if we can keep winning football matches.
"But I very much doubt it. I think it will be Celtic and then Aberdeen, but as long as we stay in the mix I'll be happy.
"One thing I will say is that we don't want to sit back and rest on our laurels, in terms of being in a cup final and still being in the Scottish Cup.
"The league campaign's our bread and butter and I feel that's where you get judged
"So to come here and pick up the victory, I'm absolutely delighted.
"There's something in the water up in Inverness, I'm serious. With this bunch of boys in that dressing room, there are no egos, no Billy big times.
"They train like that, they play like that, they live their lives like that.
"They're all in it together. We just take it as it comes. We've got a big game on Tuesday in the Highland derby and we're looking forward to it.
St Johnstone boss Tommy Wright said of the game: "We should have got something out of the game, particularly in the second half.
"We controlled large parts of it and we had the best chance of the second half.
"But we didn't start the game well. A little bit of indiscipline and some crazy decisions at times allowed them a lot of free-kicks and they put us under pressure by putting a lot of balls into the box.
"But we should have got something out of the game because in the second half we were much better than them."