When Maryland baseball starter Hunter Parsons left in the sixth inning Sunday due to an apparent right leg injury, coach Rob Vaughn had the bullpen arms he wanted thanks to an off day Saturday.

The Terps’ top four relief options were available to complete the final 3 1/3 innings against Illinois, but Vaughn’s plan derailed when catcher Justin Morris’ error on a dropped third strike allowed the Illini to plate the tying run in the seventh off left-hander Sean Fisher.

In the next frame, three relievers — right-handers Mike Vasturia, John Murphy and Kevin Biondic — issued consecutive walks to load the bases before two straight sacrifice flies put Illinois ahead, 4-2. The Illini carried that advantage to a rubber-match victory after Maryland’s offense failed to capitalize on a bases-loaded opportunity in the bottom of the eighth.

“Unfortunately, we put three guys on in a row, and they cashed in,” coach Rob Vaughn said. “We come back the next inning, put the first two guys on, and just can’t execute. Really, that’s the story of the game right there.”

The pitchers Vaughn most wanted on the mound with the game on the line fell short.

“Those are our three guys out of the pen,” Vaughn said. “They’re going to continue being our three guys out of the pen. … It didn’t line up and work, but I think we had the guys in the right positions today.”

Parsons (3-2) supplied the Terps (15-17, 3-3 Big Ten) with 5 2/3 innings, surrendering one run while striking out seven. His day was cut short after he grabbed the back of his right leg midway through the sixth with Maryland trailing 1-0.

In the bottom of the sixth, the Terps evened the score, as right fielder Jack Yalowitz bobbled second baseman Nick Dunn’s single. Vaughn gave Lee a thumbs-up after the junior slid safely into home, his aggression having created a run for Maryland’s struggling offense.

The Illini (19-8, 6-3) then gave the Terps the go-ahead run after two walks — one intentional — and a bases-loaded hit by pitch.

But key strikeouts from Morris and right fielder Randy Bednar limited the Terps’ production.

“We’re just not finishing the inning,” Vaughn said. “It doesn’t always have to be sexy, it’s just a matter of executing. We have bases loaded and one out and get a [strikeout] instead of a deep fly ball.”

With Illinois designated hitter Michael Michalak on second in the seventh, a strikeout pitch eluded Morris for a passed ball. After retrieving it, he made an errant throw to first that allowed Michalak to level the score at two, and walks from the Terps’ most reliable bullpen arms this season helped Illinois grab a two-run lead in the next frame.

Maryland failed to cash in on a bases-loaded opportunity in the eighth inning and managed only a single in the ninth, clinching its first Big Ten series loss.

“The biggest thing for us is just trying to execute in those situations,” Lee said. “The biggest thing to do that is knowing who we are as a team and as individual players. Just staying in our approach and doing what we do. It’s going to have to come eventually.”