The 29-year-old, who progressed through the Blades' youth system before making his first-team debut in 2000, has been troubled by a knee injury this season, while the club face an uphill struggle to avoid relegation after slumping into the bottom three at the beginning of last month.
Montgomery said: "This has been the most disappointing season in my 12 years at the club.
"We've had four managers this season and that says it all, but as a bunch of lads we have to stick together and we still have the belief that we can do it.
"If we can come through this, it would probably be a bigger achievement than promotion to the Premier League in 2006 because everything is stacked against us."
Source: PA
Source: PA