"[Simon] went back to see the doctor, and we're going to have a decision by [Wednesday]," said Walt Jocketty, president of baseball operations.
Simon last pitched on June 15, throwing two innings in an extra-innings loss at Atlanta. Following a hitless bottom of the 12th, the Braves got to him for three runs and five hits in the bottom of the 13th to walk off with a victory. It was Simon's second relief outing of the season but his first since being removed from the rotation after season-long struggles.
It would not be a big leap of faith to expect Lorenzen to take Simon's spot on the roster should Simon be placed on the DL. Lorenzen has been out since early March with a sprained right elbow; contracting mononucleosis in early April further set him back.
Expected to compete for a rotation spot before the season, Lorenzen will instead work out of the bullpen. He made four appearances during a rehab assignment at Triple-A Louisville, with four scoreless innings, two hits, no walks and seven strikeouts.
"Everything has gone smoothly, gone perfectly after the whole mono thing," Lorenzen said.
The Reds are waiting an extra day to activate Lorenzen because they wanted to give him two full days of rest after he pitched back-to-back games on Saturday and Sunday for Louisville. An additional roster move will be required to add him to the 40-man roster.
Lorenzen, who gained back the 20 pounds he lost while he was ill, has accepted his role as a reliever.
"I prepare myself to be the best baseball player I can possibly be," he said. "I show up and I say, 'Wherever you need, that's where I go.'"
The 24-year-old Lorenzen made 21 starts last season in his rookie year and had a 5.40 ERA in 27 games. He's waited a long time to begin his second big league season but isn't nervous about making his 2016 debut.
"I have visualized this since the offseason. I'm ready," he said. "I've been here before, multiple times. I've been visualizing it. I'm ready. There are no jitters. It's more of a freedom than anything. I'm finally free. I've put the work in. Now it's time to go out there and express myself the way I best know how to."
Mark Sheldon has covered the Reds for MLB.com since 2006, and previously covered the Twins from 2001-05. Read his blog, Mark My Word, follow him on Twitter @m_sheldon and Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.