Cleansing worker Paul Donohoe, 54, told the High Court in Glasgow that his colleague called an ambulance for 76-year-old John Baker.
He said the injured man had called out: "I've got a bad heart, I can't breathe right", before passing out.
Peter Telfer, 25, denies murdering Mr Baker in the Calton area on 29 June 2016.
Mr Telfer is also accused of assaulting and attempting to rob shop worker Owaisuddin Siddique and carrying a knife on 24 June.
He also faces a string of charges including behaving in a threatening or abusive manner at various streets in Glasgow city centre and assaulting and robbing two women of their handbags on 28 June.
Mr Telfer allegedly attempted to defeat the ends of justice, and has also been charged with possessing cannabis.
Giving evidence at the trial, Mr Donohoe described how he and his two colleagues were told by John Baker "I've been stabbed".
A recording of the 999 call made by his colleague Alan Miller was played to jurors.
One of the workmen can be heard on a recording to the emergency services saying there was "blood coming from his mouth" and "I can't feel a pulse".
A voice in the background could be heard saying there were two wounds on Mr Baker's back and he was having "trouble breathing".
The trial before judge Lord Matthews continues.
A dying man flagged down a refuse truck for help after being attacked in a Glasgow street, a court has heard.