The Giants SHOULDN'T bench Eli Manning -- they should block for his ass -- 'cause he's still a great QB ... so says the guy who won 2 Super Bowls with the embattled star.
TMZ Sports talked to Brandon Jacobs -- Eli's NYG teammate from 2005-2011 -- about the 1-5 Giants' crappy offense ... and whether it's time to put Manning on the pine.
"I still think right now, I think Eli is great."
B.J. says Eli's gotta be used right, 'cause he ain't the guy to operate a run-and-gun style offense.