The Parkhead manager has alternated between Sam Johnstone and Viljami Sinisalo, with Johnstone joining on loan from Wolves to compete with Sinisalo.

Sinisalo, who was Kasper Schmeichel's understudy last season, played a string of games towards the end of the campaign after the Dane was injured.

Johnstone was pitched in after his arrival, but Sinisalo was reinstated for a run of games before the pair were switched over again.

O'Neill was satisfied with the 33-year-old's performance against Dundee United but admitted a decision is still to be made on the number one.

He said: "Sam, yeah, I thought he did fine, really fine in the game.

"So it'll take us a few weeks before we find out who will stay in goal for hopefully the rest of the season."

After conceding two goals in three minutes to fall behind in the game, Celtic now have one clean sheet in their last eight matches.

The 74-year-old admitted: "I think naturally we can do better.

"I think that we could have done better for the goals.

"But every single goal that's conceded, every manager and every player on the team that's conceded will say that he could have done better."

There is also a concern around the lack of control they have in matches.

O'Neill added: "Yeah, I think, I think sometimes the lack of control comes from, you know, losing possession quite easily.

"Sometimes the move breaks down.

"Next thing you know that we're stranded because we are essentially at Celtic Park controlling the game, controlling it."