The original definition from beamerbaseauxtemplates.sty
is
\defbeamertemplate{footline}{frame number}
{
\hfill%
\usebeamercolor[fg]{page number in head/foot}%
\usebeamerfont{page number in head/foot}%
\insertframenumber\,/\,\inserttotalframenumber\kern1em\vskip2pt%
}
So if you want to keep colour, character position etc., try with
\setbeamertemplate{footline}{%
\hfill%
\usebeamercolor[fg]{page number in head/foot}%
\usebeamerfont{page number in head/foot}%
\insertframenumber%
%\,/\,\inserttotalframenumber
\kern1em\vskip2pt%
}
But I'm not sure if this fulfils you not "tex level or producing a new command" requirements, whatever this means.
With an up-to-date version of beamer, this can be simplified to
\setbeamertemplate{footline}{
\hfill%
\usebeamercolor[fg]{page number in head/foot}%
\usebeamerfont{page number in head/foot}%
\setbeamertemplate{page number in head/foot}[framenumber]%
\usebeamertemplate*{page number in head/foot}\kern1em\vskip2pt%
}
\setbeamertemplate {footline}{\quad\hfill\insertframenumber\strut\quad}