PITTSBURGH -- The Pirates' rotation plans came into clearer focus before and after their 4-0 loss to the Phillies at PNC Park on Friday.
After the game, manager Clint Hurdle made official what had been expected all week: Top prospect Tyler Glasnow will make his home debut against the Phillies at 4:05 p.m. ET on Saturday afternoon for his second Major League start.
Glasnow was on turn to pitch for Triple-A Indianapolis on Saturday, but right-hander Chad Kuhl assumed his place after being sent down earlier this week to make room in the rotation for Jameson Taillon. So Glasnow will rejoin the Pirates, perhaps this time to stay.
The Pirates will be throwing their top three pitching prospects in recent memory in the same series: Gerrit Cole on Friday, Glasnow on Saturday and Taillon on Sunday.
Glasnow was charged with four runs on three hits and two walks while striking out five over 5 1/3 innings in his Major League debut against the Cardinals on July 7. He is 7-3 with a 1.94 ERA and 122 strikeouts over 102 innings for Indianapolis.
Before Friday's game, Hurdle revealed that Pittsburgh plans to start Francisco Liriano and Cole next week against Seattle at PNC Park. That two-game series will take place between two off-days, allowing the Bucs to skip struggling lefty Jeff Locke's scheduled start.
Locke will be available out of the bullpen on Saturday and Sunday, Hurdle said. It's unclear if the assignment will last longer, but the Pirates could go until Aug. 6 without a fifth starter if they keep four starters -- Liriano, Cole, Glasnow and Taillon -- working on regular rest around their upcoming off-days.
New look up top
Shortstop Jordy Mercer, the Pirates' primary leadoff man against left-handed starters this season, found himself atop the order against Phillies righty Zach Eflin on Friday. Mercer went 0-for-4 in his first Major League start batting leadoff against a right-hander. 
"I showed up today and I was No. 1," Mercer said, smiling. "It stays the same. You want to get on base because you've got some guys that are going to hit you around. It's not going to change the way I do anything. It's just weird to see my name up there again at the top. That's about it."
Hurdle cited Mercer's performance at PNC Park this season -- he's hitting .318/.394/.439 in 46 games -- as well as his .350 on-base percentage and Eflin's splits against right-handed hitters.

First baseman John Jaso, previously Pittsburgh's leadoff man against right-handers, batted fifth on Friday. Jaso is hitting .212/.299/.292 since June 1.
"I'm trying to leave John in a different scenario and looking for another guy to plug in," Hurdle said. "I was much more drawn to giving Mercer the opportunity than anybody else.
"I'm not so sure it's pressure. It's just a different look. That's all I had for [Jaso]. 'This isn't scientific, and I can't overcook it. I just want you to hit somewhere different.'"
Jaso responded well to the move, going 2-for-3 with a double against the otherwise-unhittable Eflin. For all the talk of getting Jaso out of the leadoff spot, both of his hits on Friday led off an inning.
"It was pretty funny how that worked out," Jaso said. "This game is strange."
Roster move
Veteran catcher Erik Kratz elected free agency on Friday after clearing waivers and declining an outright assignment to Triple-A Indianapolis.
Kratz was designated for assignment on Tuesday when the Pirates brought Francisco Cervelli off the disabled list. He hit .107 with a homer and four RBIs in 18 games for the Pirates.