Marmolejos, 24, connected on his third homer in a 3-for-4 performance on Wednesday, hitting a two-run shot in the third inning that would prove the difference in Double-A Harrisburg's 6-5 win over Erie. After opening the season on the disabled list with a hand injury, Marmolejos has notched hits in 10 of 11 games, including eight straight, for the Senators, during which he's batting .413/.451/.696 with seven extra-base hits and 12 RBIs.
Kopech, ranked 13th on MLBPipeline.com's Top 100 Prospects list, completed a season-high seven innings, allowing one earned run on three hits, in his last turn for Double-A Birmingham. The 21-year-old righty fanned eight -- the fifth time in eight starts he's achieved that total -- in the outing and enters Thursday with 59 strikeouts in 42 1/3 innings (12.5 K/9), as well as a 2.76 ERA and a .145 opponents' average.
Giolito has struggled this season in his return to the Triple-A level, posting a 1-5 record with a 6.41 ERA in eight starts for Charlotte, though he has fared somewhat better of late, logging a 4.09 ERA in his last 11 frames (two starts). Control remains an issue for the No. 8 overall prospect, who's issued 22 walks and allowed 42 hits (1.63 WHIP) while striking out 40 in 39 1/3 innings.
Voth, meanwhile, will look to build off a stretch in which he's allowed exactly two earned runs in three straight starts to lower his ERA to 4.73 from 5.63. But like Giolito, the 24-year-old righty has struggled with his efficiency, posting a 31-to-20 strikeout-to-walk ratio and allowing a .302/.379/.438 opposing slash line -- fueled by a .352/.418/.437 line by left-handed hitters -- in 40 innings (eight starts).
Thursday's Top 100 prospect probables
No. 37 Braxton Garrett (Marlins' No. 1), Greensboro vs. Kannapolis (7 p.m. ET)
No. 76 Grant Holmes (A's No. 3), Midland at Arkansas (8:10 p.m. ET on MiLB.TV)
No. 77 Ian Anderson (Braves' No. 6), Rome at Augusta (7:05 p.m. ET)
No. 87 Cal Quantrill (Padres' No. 2), Lake Elsinore vs. Inland Empire (10 p.m. ET)
No. 98 Chance Adams (Yankees' No. 7), Scranton/Wilkes-Barre at Columbus (6:35 p.m. ET on MiLB.TV)
More top prospect probables
Andrew Moore (Mariners' No. 4), Tacoma vs. Fresno (Triple-A) Gabriel Ynoa (Orioles' No. 11), Norfolk at Toledo (Triple-A)
Marco Gonzalez (Cardinals' No. 19), Memphis at Sacramento (Triple-A) Clay Holmes (Pirates' No. 19), Indianapolis at Lehigh Valley (Triple-A) Frank Duncan (D-backs' No. 24), Reno at Iowa (Triple-A)
Ariel Jurado (Rangers' No. 3), Frisco at NW Arkansas (Double-A)
Brad Keller (D-backs' No. 7), Jackson at Jacksonville (Double-A)
Dakota Hudson (Cardinals' No. 9), Springfield at Corpus Christi (Double-A)
Brandon Waddell (Pirates' No. 16), Altoona vs. Akron (Double-A) Lucas Sims (Braves' No. 18), Gwinnett vs. Buffalo (Double-A) Drew Anderson (Phillies' No. 21), Reading at Trenton (Double-A)
Parker French (Rockies' No. 21), Hartford at Bowie (Double-A)
Artie Lewicki (Tigers' No. 21), Erie vs. Harrisburg (Double-A)
Trey Ball (Red Sox's No. 29), Portland at New Hampshire (Double-A)
Beau Burrows (Tigers' No. 3), Lakeland vs. Palm Beach (Class A Advanced)
Scott Blewett (Royals' No. 4) vs. Shane Bieber (Indians' No. 16), Wilmington vs. Lynchburg (Class A Advanced)
Oscar De La Cruz (Cubs' No. 5), Myrtle Beach vs. Winston-Salem (Class A Advanced)
Peter Lambert (Rockies' No. 7) vs. Matt Krook (Giants' No. 12), Lancaster vs. San Jose (Class A Advanced) Albert Abreu (Yankees' No. 10), Tampa at Jupiter, Game 2 (Class A Advanced) Touki Toussaint (Braves' No. 11), Florida vs. Clearwater (Class A Advanced) Freddy Peralta (Brewers' No. 19), Carolina at Down East (Class A Advanced)
Brian Gonzalez (Orioles' No. 19), Frederick at Potomac (Class A Advanced)
Ian Clarkin (Yankees' No. 20), Tampa at Jupiter (Class A Advanced)
Justin Donatella (D-backs' No. 26), Visalia vs. Stockton (Class A Advanced)
Genesis Cabrera (Rays' No. 28), Charlotte vs. Daytona (Class A Advanced)
Luis Escobar (Pirates' No. 13), West Virginia vs. Hagerstown (Class A)
Merandy Gonzalez (Mets' No. 14), Columbia at Lexington (Class A)
Adonis Medina (Phillies' No. 15), Lakewood vs. Delmarva (Class A)
Micah Miniard (Indians' No. 29), Lake County at Lansing (Class A)
Mike Rosenbaum is a reporter for MLB.com. Follow him on Twitter at @GoldenSombrero. This story was not subject to the approval of Major League Baseball or its clubs.