Rafael Benitez insisted he cannot even think about a takeover of Newcastle and the cash it could hand him as he attempts to prevent their season from unravelling.
The promoted Magpies slipped to within two points of the Premier League relegation zone after Leicester condemned them to a sixth defeat in seven games with a last-gasp winner at St James' Park.
Former Newcastle skipper Alan Shearer summed up the frustration of many among a crowd of 52,117 after the game in a tweet directed at owner Mike Ashley, as he continues talks with prospective buyer Amanda Staveley's PCP Capital Partners.
Shearer wrote: "Nowhere near good enough @NUFC today. Sell our club Mr Ashley to someone who wants to be here before it's too late again."
However, when asked if the defeat means investment in January is imperative, Benitez said: "After a game is not the time for me to talk about that.
"What I can say is the players, they put in an effort on the pitch, but still we have to improve if we want to get three points in these kind of games.
"We have paid in the past two or three games for easy mistakes and we have to learn quickly."
Newcastle thought they had snatched at least a point when Dwight Gayle saw his 73rd-minute shot deflected past Kasper Schmeichel by Harry Maguire to make it 2-2.
But their hopes were dashed at the death when they were caught on the counter-attack and Ayoze Perez fired into his own net as he attempted to prevent fellow substitute Shinji Okazaki from scoring.
The Foxes had earlier bounced back from Joselu's fifth-minute opener to lead through goals from Riyad Mahrez and Demarai Gray.
Benitez said: "I said that it could be like this and we have to understand that the only way is keep working harder and don't make these kind of mistakes."
Foxes boss Claude Puel was delighted with the efforts of his players to bounce back from the disappointment on conceding the first goal and then Gayle's equaliser to secure a third successive league win.
He said: "I think we deserved this win with a fantastic positive attitude. It was a difficult game - we had to play against Newcastle and against this atmosphere, and it's always difficult to play, to resist sometimes under pressure.
"The second goal gave us the lead, but it was difficult, but a draw would have been difficult to accept, so my team deserved the third goal with a fantastic and positive attitude."
Puel reserved particular praise for Japan international Okazaki, who forced the winner after playing on following a head wound which left him swathed in bandages.
He said: "The first example is Shinji - he is a kamikaze and it's a good thing for the team. He's a fantastic player with fantastic spirit and all the squad like him because he gives everything and he also gives his body for the team."