But rookie pitchers are about all any Padre opponent will be facing for the rest of this season with Tuesday's announcement that veteran left-hander Clayton Richard will miss the rest of the season as he awaits surgery on his left knee.
With Richard out, the dean of Padres starters in the current rotation is left-hander Robbie Erlin with 32 career starts, including seven this season. No. 2 on the list is Lucchesi with 20 starts followed by Eric Lauer (18), Nix (four) and Brett Kennedy (four).
And more rookie starters could be added to the mix as the Padres look toward 2019, 2020 and beyond with hopes they can avoid a 100-loss season in 2018.
The left-handed Lauer is expected to be activated from the disabled list later in the week to fall into line with right-hander Nix, Lucchesi, right-hander Kennedy and Erlin.
Lucchesi (6-7, 3.74 ERA) will be matched against Mariners right-hander Erasmo Ramirez (1-2, 4.50 ERA) in Wednesday's finale of a short two-game series. Lucchesi will be making his first appearance against the Mariners.
Lucchesi, 25, the Padres' fourth-round pick in the 2016 draft, has blown hot-and-cold in six starts since spending the All-Star break with Triple-A El Paso. He has allowed two or fewer runs in four starts and five runs in each of the other two starts.
Lucchesi owns a 4.59 ERA in those six starts, although he allowed only two runs on five hits and a walk with six strikeouts in six innings in his most recent start at Colorado on Aug. 23.
Lucchesi has the lowest ERA among Padres' pitchers with at least 20 starts. His 35 walks are the eighth-fewest among any National League pitcher with at least 20 starts.
Wednesday will be Lucchesi's third start against an American League team. He has already faced Oakland and Texas with a 0-1 record and a 6.35 ERA. The Padres are 9-11 in Lucchesi's first 20 starts.
Ramirez has faced the Padres three times in his Major League career that started in 2012. But the 28-year-old from Nicaragua hasn't faced the Padres since 2016. Overall, Ramirez is 0-1 against the Padres with a 3.75 ERA over 12 innings in two starts and one relief appearance.
His best outing against the Padres came in his only previous appearance at Petco Park during the 2014 season. He allowed two hits and two walks with three strikeouts over six shutout innings.
Ramirez will be making his third start since returning from the disabled list on Aug. 11. He had been out since May 1 with a shoulder strain. This is only Ramirez's sixth start of the season. Over the first five, he has allowed 15 runs (13 earned) on 27 hits and six walks with 18 strikeouts in 25 2/3 innings.
Beyond Wednesday, the Padres haven't established a rotation order for the rest of their homestand, which concludes with four games against the Colorado Rockies.