Romero surrendered eight runs on five hits and three walks while recording just two outs. He threw just 13 of his 32 pitches for strikes, as his well-documented control issues continued to plague him.
The 28-year-old Romero now owns a 13.85 ERA in four starts with the Bisons. He's allowed 23 hits and 20 walks in just 13 innings of work, and the Blue Jays have to be wondering what steps they can take from here.
Romero was cut by the Blue Jays at the end of Spring Training to overhaul his mechanics on the mound. He spent almost a month in extended spring training in an effort to change his delivery and limit the way he throws across his body.
The native of East Los Angeles had one encouraging outing for Class A Dunedin before being promoted to the Major League level. That stint lasted just two starts, as he allowed six runs in 4 1/3 innings before being sent down on May 9.
While Romero struggles to find his previous form, right-hander Dustin McGowan continues to make progress in his comeback from a right-shoulder injury. McGowan, who is currently on the 60-day disabled list, also pitched for Triple-A Buffalo on Monday night.
McGowan allowed one run on one hit and one walk while striking out three over two innings of work. He threw 20 of his 33 pitches for strikes, but there is no immediate timeframe on when he will be ready to re-join the Blue Jays.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.