Matthew Stafford better have brought his tough-guy helmet with him to Detroit this weekend ... 'cause Calvin Johnson tells TMZ Sports he's not expecting Lions fans to welcome their former QB with open arms.
Of course, Megatron says there will likely be some cheers and even some people decked out in Stafford's former No. 9 jerseys at Ford Field when the Rams visit for their much-anticipated Wild Card round game Sunday night ... but the Hall of Famer tells us, "I'm sure there will be people booing."
As for how Johnson will feel .