The 25-year-old England winger has found the going tough on Wearside since announcing his arrival from Manchester City in a thrilling debut in a 2-0 Capital One Cup victory over Morecambe on August 28.
Much has been expected of O'Neill's £10million summer acquisition and he is yet to find his feet on a sustained basis with a thigh injury having hampered his attempts to rediscover his best form.
However, the manager, who takes his team to Stoke on Saturday, is confident a run of games now the international breaks have ended for the calendar year will help Johnson establish himself as the star he believes he will be.
O'Neill said: "First of all when he arrived here, his opening game against Morecambe was fantastic, he played really well in the game.
"Then we travelled down to Swansea and he couldn't really get into it, and since that he went with England, got injured, came back with us, missed games when he was hoping to be fit and his thigh injury was still niggling, and there's nothing more frustrating and more annoying if you are a person who has not been injured that often.
"That has had some sort of an effect. Once he gets a run, he will be fine.
"Coming here and maybe feeling that everybody is expecting him just to win games on his own - it's a thought.
"It's not necessarily what I actually believe, but it's a thought, and perhaps that's something that he should concern himself less with."
Johnson is one of a series of talented men who have under-performed in recent weeks with he, James McClean and Stephane Sessegnon in particular having failed to make any real impact in Sunday's derby draw with Newcastle despite the Magpies playing the final 65 minutes with only 10 men.
As a result, striker Steven Fletcher, the only Sunderland player to have scored a league goal for the club so far this season, found himself isolated.
It is a problem O'Neill acknowledged himself in the aftermath of the game, but he is certain time is all that is required.
He said: "It's up to me to be able to change those things and get players performing, that's my job.
"I am sure in the course of time - and when I say the course of time, I don't mean six months' time...but we are not a million miles away, I think."
The return of skipper Lee Cattermole from his latest suspension and full-back Phil Bardsley's availability after missing the start of the season with an ankle injury, mean O'Neill has options this weekend.
Were Bardsley to be selected, that would free up emergency right-back Craig Gardner to return to the midfield role he prefers and allow the manager to reshuffle if he felt the need.
Asked if he would consider taking one or more of his stuttering flair players out of the firing line, he replied: "Over the course of time, I will see, but we will certainly have to change the squad around a bit.
"For instance, we played on Sunday, we play again on Saturday and then we have got a game against Middlesbrough coming up, so it is likely that the side would have to be changed around a little bit, bearing in mind, of course, the games are very, very important to us.
"But in the scheme of things as we speak now at this minute, of course I would like our really good players to be playing a bit better, but it's not as major a concern at the moment to me as you would think."
A trip to Stoke is never easy at the best of times, but with snow forecast this weekend, it could be even more testing, although having won 1-0 at the Britannia Stadium in February in similar conditions, Sunderland at least have experience to fall back on.
O'Neill said: "The conditions at Stoke that day were really surreal.
"They cleared some of the snow off the pitch early on, but then down came a flurry with 10 or 12 minutes to go and had that arrived let's say even 15 minutes earlier, there's no way the game would have been finished."