BOSTON — The Boston Red Sox have shifted personnel in their bullpen after a trade early Saturday, followed by the news that closer Craig Kimbrel will miss 3-6 weeks with a knee injury.

Kimbrel will undergo surgery Monday for a torn meniscus in his left knee. Kimbrel had been selected to the All-Star Game after recording 17 saves for Boston.

The announcement about Kimbrel came after Boston traded two low level minor leaguers to the Arizona Diamondbacks for right-handed reliever Brad Ziegler. That deal was completed at 2 a.m. Saturday. Red Sox president Dave Dombrowski said the trade was already in the works before the team learned about Kimbrel.

Ziegler, 36, had a 2-3 record for Arizona, with a 2.82 ERA and 18 saves in 36 relief appearances. A side-arm pitcher, Ziegler held right-handed batters to a .266 average. Even though he was being obtained to be a set-up reliever, Boston Manager John Farrell said Ziegler may also handle some closing duties, along with Koji Uehara.

To make room for Ziegler on the Red Sox 40-man roster, catcher/outfielder Blake Swihart was transferred to the 60-day disabled list. Ziegler was due to arrive in Boston by 6 p.m. on Saturday.

The minor leaguers traded to Arizona were both playing for low Class A Greenville – right-handed pitcher Joe Almonte and infielder Luis Alejandro Basabe. Both Almonte and Basabe were international free agents, in their fourth season with the Red Sox. Basabe, 19, was hitting .311 this season. Almonte, 20, had a 2-2 record with a 3.91 ERA in 10 starts.

In another move Saturday, the Red Sox activated recently-obtained infielder Michael Martinez to the roster and sent Marco Hernandez back to Pawtucket.