Turns out the injuries to John Lackey and Hector Rondon are a bit more serious than first thought:
#Cubs to promote Rob Zastryzny to big league team today— Carrie Muskat (@CarrieMuskat) August 19, 2016
Looks like Lackey and Rondon headed to DL. Zastryzny and Pena to be called up. #Cubs— Carrie Muskat (@CarrieMuskat) August 19, 2016
Lackey was tentatively scheduled to start Tuesday against the Padres; that start could be taken by Jake Arrieta on normal rest.
Lackey had some shoulder fatigue during his last start, and Rondon had pitched just once since he was bothered by tricep tightness earlier this month. Neither injury sounds serious; hopefully, this just gives both of these pitchers time to rest. They won't be eligible to return until after September 1, so when rosters expand and they do return, no one will have to be removed from the roster. That's confirmed here:
The moves re Rondon and Lackey are precautionary more than anything. #Cubs— Carrie Muskat (@CarrieMuskat) August 19, 2016
With the #Cubs lead in Central they have luxury of being careful with Rondon and Lackey— Carrie Muskat (@CarrieMuskat) August 19, 2016
Rob Zastryzny was the Cubs' second-round pick in the 2013 draft. He's been mostly a starter at Double-A Tennessee and Triple-A Iowa, making 24 appearances (23 starts) with a 4.71 ERA. He seems to be the kind of pitcher who would be quite effective as a LOOGY.
Felix Pena, a righthander, was signed by the Cubs out of the Dominican Republic in 2009, and he's steadily moved up the organizational ladder. This year at Iowa he's made 36 relief appearances, posting a 3.41 ERA with 81 strikeouts in 63⅓ innings.
This also means that Mike Montgomery might make more than just one start, replacing Lackey. Or the Cubs could give Trevor Cahill another start. They do have an off day next Thursday, so they could conceivably skip that turn in the rotation, too.
The Cubs' 40-man roster stands at 39. Neither of these players is currently on the 40-man, but the Cubs could move Dallas Beeler and/or Aaron Brooks to the 60-day DL (both have been out all year) to make room on the 40-man.