Ray (3-1, 3.25 ERA), one of the hottest pitchers in the National League, will pursue a ninth consecutive start without a defeat when he opposes Giants left-hander Drew Pomeranz (1-4, 5.66) in the series opener.
Pomeranz has been on the opposite end of the success spectrum from Ray, having allowed 12 runs in just 10 1/3 innings in his last three starts.
Just sending Pomeranz to the mound already has proven costly for the Giants, who activated the 30-year-old from the injured list in order for him to start at Arizona last Sunday. Pomeranz had been out with a strained lat.
In order to create a roster spot, the Giants designated Aaron Altherr for assignment, making him available to other teams on a waiver claim. Sure enough, the New York Mets claimed the outfielder on Thursday, ending his San Francisco career with just one at-bat.
"You pull for these guys to be in the big leagues," Giants manager Bruce Bochy said of Altherr, whom the club had hoped to send to Triple-A to store him for a potential future recall. "Good for him.
"Selfishly, though, we would have loved to have him in our system and just give him some at-bats (at Sacramento). That's what he needs right now -- reps. The Mets obviously see him the way we saw him. He's a guy with tremendous potential."
Pomeranz limited the Diamondbacks to two runs in 4 2/3 innings in a 3-2 win in Arizona last weekend in an another head-to-head with Ray. Neither starter got a decision.
Pomeranz has rarely experienced any measure of success against the Diamondbacks, going 0-3 with a 7.76 ERA in nine games, including six starts.
The good news for the first-year Giant is the Diamondbacks no longer employ Paul Goldschmidt, a longtime pain in his side. While with Arizona, Goldschmidt went 6-for-12 against Pomeranz with three doubles, a home run and five RBIs.
Suffice it to say, no Giant has had close to that kind of success against Ray, who has gone 4-1 with a 2.98 ERA in 12 starts against the National League West rival.
He's been even better in San Francisco, recording a 3-1 record and 2.15 ERA in five starts.
Ray is being moved up a spot in the rotation because the Diamondbacks have demoted Zack Godley to the bullpen. Right-hander Taylor Clarke is expected to be promoted from Triple-A to join the rotation, but he'll be slotted after Ray on Saturday.
As the Diamondbacks attempt to reverse a five-game losing streak, they will play Friday night without manager Torey Lovullo, who will be attending his son Connor's high school graduation.
He is slated to rejoin the team Saturday, by which point shortstop Nick Ahmed hopes his club already has one win in the three-game set.
"We got off to a good start to the season," he told reporters after Wednesday's 5-2 loss at San Diego that capped a three-game sweep. "That allows you to handle a stretch like this and still have a good season. We're going to bounce back."
The Giants have lost two straight after falling 5-4 to Atlanta in i13 innings on Thursday.