The 25-year-old Lyons won his first two career starts but was 0-3 in his last four and is 2-3 with a 5.51 ERA. He was a ninth-round pick in 2010.
"He needs to control the strike zone with his fastball," Matheny said. "We gave him a list of a couple of little things to work on, but for the most part it has everything to do with fastball location."
Right-hander Michael Blazek, a 35th-round draft pick in 2007, was recalled to add bullpen depth. The 24-year-old Blazek made it to the majors for the first time earlier in the season but did not appear in a game, and had a 2.31 ERA and one save at Memphis in eight games with four of his outings lasting two innings.
He began the year at Double-A Springfield, where he had a 0.92 ERA with 25 strikeouts in 19 2-3 innings.