SF Giants add potential high-leverage reliever to the bullpen

Division Series - Los Angeles Dodgers v San Diego Padres - Game Three
Division Series - Los Angeles Dodgers v San Diego Padres - Game Three / Tom Pennington/GettyImages

The SF Giants were likely going to upgrade the bullpen at the trade deadline but they did so in an unexpected way on Thursday. The team announced that they had agreed to terms on a one-year, $4.5 million pact with veteran reliever Trevor Rosenthal.

SF Giants add potential high-leverage reliever to the bullpen

The 40-man roster was full at the time of the signing, so the Giants transferred Mauricio Llovera to the 60-day injured list after sustaining a flexor strain right before the All-Star break. Rosenthal was added and immediately placed on the 15-day injured list with a hamstring strain.

That move is likely to give Rosenthal an opportunity to get his arm into shape by means of a rehab assignment.

The righty was selected in the 21st round of the 2009 draft by the St. Louis Cardinals out of Cowley Community College in Arkansas City, Kansas. Rosenthal knows the Giants well as he was on the losing end of the NLCS against them in both 2012 and 2014.

Since he debuted in 2012, the 32-year-old reliever has established himself as one of the better relievers over the past decade. In his career, Rosenthal has registered a 3.36 ERA, 2.75 FIP, 1.32 WHIP, 12.1 K/9, and a 2.77 SO/W ratio with 132 saves.

However, he has been slowed by injuries in recent seasons. The veteran reliever underwent Tommy John surgery at the end of 2017 that knocked him out for the entire 2018 season. He struggled in his return, posting a 13.50 ERA in 15 appearances split between the Washington Nations and the Detroit Tigers.

The eight-year veteran rebounded nicely in 2020 where recorded a 1.90 ERA with 38 strikeouts against only eight walks in 23.2 frames with both the Kansas City Royals and the San Diego Padres. The Oakland A's signed Rosenthal to a one-year, $11 million deal in 2021 but he never made an appearance with the team.

As the season was getting underway, the righty underwent thoracic outlet surgery after experiencing numbness in his hands and fingers. Rosenthal held a showcase in June of this year, and the Giants must have been impressed by what they saw. When he is healthy, the former Cardinals reliever flashes a fastball in the high-90's that he pairs with an above-average slider.

That said, the track record for pitchers fully recovering from both Tommy John surgery and thoracic outlet surgery is not great. There is an element of risk in signing him.

However, the cost was purely financial, so the Giants added a reliever with good upside in the middle of the season without giving up prospect capital. If he can regain the effectiveness he once had, Rosenthal would immediately become one of the Giants' better high-leverage relievers.