The lefty finished the day having allowed five runs on four hits in 5 2/3 innings for the loss, his first of the season.
While Rodriguez's fastball velocity consistently hovered in the mid-90s, Red Sox pitching coach Carl Willis said he would have liked to see the left-hander use more secondary pitches.
"With Eddie today, he's sitting mostly 93, 94, and that's a good fastball and he has life with that fastball, but at the same time, these hitters at this level, they see that on a daily basis," Willis said. "You have to be able to disrupt their balance. He has the weapons to do that. I think today, he got a little bit in a mindset of not wanting to make a mistake with secondary pitches to allow that to happen, and it made it a little easier for them when he made a mistake with the fastball."
Against a heavily right-handed power-hitting lineup, Rodriguez said his goal was to stay on the outer half of the plate. It was when those pitches leaked out over the middle of the plate that he got burned.
Rodriguez was on point in his first start of the season on Tuesday against the Orioles, allowing two runs on six hits in six innings for the win.
Sunday's outing snapped an eight-game streak of the left-hander allowing three or fewer earned runs. He also hadn't allowed more than two home runs in any of his 22 career starts.
It's been a slow process in getting back to the Majors for Rodriguez after he dislocated his right kneecap at the beginning of Spring Training.
"He's been through a lot this year," Willis said. "It's been like a four-month Spring Training almost. Even the rehab outings he goes through in the Minors, that's nothing like pitching in the Majors, nothing like pitching in Fenway Park, and then of course you couple that with facing the Toronto Blue Jays, in our division, very formidable lineup. So he's trying to be aggressive, and yet there in the back of his mind he's trying to stay careful as well. He needs to stay more on the aggressive side of that thought process."
Willis said he noticed some inconsistencies in Rodriguez's delivery during the start that he hopes they can work through before the left-hander's next outing.
"It's his second start at the big league level," Willis said. "So does he have to be better? Yeah. But at the same time, I think we saw some positive things as well."
Quinn Roberts is a reporter based in Boston for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.