Henry Ruggs was just ordered to show up in court next Monday ... after a judge said the former Las Vegas Raiders star missed a required breath test.

The NFL player's attorneys were in court Wednesday over a separate matter in the DUI crash case ... when the judge presiding over the hearing said Ruggs did not properly submit a breath test earlier this month.

As part of the conditions of Ruggs' release ... the 22-year-old must submit to alcohol testing several times a day -- but the judge said he missed one of his required check-ins.