Texas Rangers

The Texas Rangers selected Eickhoff in the 15th round of the 2011 MLB Draft, and he agreed to nullify his National Letter of Intent with Western Kentucky in order to sign with the Rangers.^[12] He was initially assigned to the Rookie Arizona League Rangers, but was promoted to the Class A Short-Season Spokane Indians of the Northwest League after only four games. In 14 appearances between Arizona and Spokane, Eickhoff was 1–2 in his rookie season, with a 2.37 ERA and 22 strikeouts in 19 innings pitched.^[11]

In 2012, Eickhoff pitched for the Class A Hickory Crawdads of the South Atlantic League.^[13] He was 13–7 with a 4.69 ERA — his 13 wins were third in the league and matched the 2nd-highest single-season win total in team history.^[13][14][15]

Eickhoff started 2013 with the Class A-Advanced Myrtle Beach Pelicans of the Carolina League, and was promoted to the Double-A Frisco RoughRiders of the Texas League during the season.^[16][17] He had the 3rd-lowest WHIP (1.17) and the 8th-lowest ERA (3.41) in the Carolina League, and his 11 wild pitches were 6th in the league.^[15]

Eickhoff returned to Frisco in 2014, where he was named Pitcher of the Week, on May 5.^[18][13] Eickhoff's 144 strikeouts and 12 wild pitches with Frisco led the Texas League, and his 1.17 WHIP was 4th-best in the league.^[19][15]

In 2015, between Frisco, the Round Rock Express, and the Lehigh Valley IronPigs, Eickhoff was 12–5, with a 3.85 ERA, and 126 strikeouts, in 133.1 innings.^[13] In 2017, with the Reading Fightin Phils he was 0–1 with a 1.80 ERA in one start.^[20] In 2018, with the Clearwater Threshers, Reading, and Lehigh Valley he was 0–1 with a 2.90 in eight starts.^[20] In 2019, with Clearwater, Reading, and Lehigh Valley he was 3–2 with a 5.93 ERA in eight starts.^[20]

Philadelphia Phillies

On July 31, 2015, the Rangers traded Eickhoff, Nick Williams, Matt Harrison, Jake Thompson, Alec Asher, and Jorge Alfaro to the Philadelphia Phillies for Cole Hamels and Jake Diekman.^[21] He made his major league debut for the Phillies on August 21. Eickhoff's 2015 big league pitching totals included a 3-3 win–loss record with a 2.65 ERA, while he struck out 49 batters in 51 innings pitched.^[2]

In 2016 (his first full season with the Phillies), Eickhoff was 11–14, with a 3.65 ERA, gave up 1.92 walks per 9 innings pitched (4th in the National League), had 20 quality starts (tied for 6th), struck out 167 batters in 197.1 innings (8th), and had a strikeout-to-walk ratio of 3.976 (9th).^[2]

In 2017, Eickhoff was 4–8, with a 4.71 ERA, and struck out 118 batters, in 128 innings.^[2] He held opposing hitters to a .218 batting average with runners in scoring position, the 6th-lowest average among NL pitchers.^[15] Eickhoff missed the end of the 2017 season because he was experiencing numbness in his fingers.^[22]

In 2018, Eickhoff was 0–1, with a 6.75 ERA, and struck out 11 batters in 5.1 innings.^[2] In a game on September 28, against Atlanta, he tied a Phillies franchise record shared by Steve Carlton in 1981 and Curt Schilling in 1996 (later broken by Aaron Nola in 2021) by striking out seven consecutive batters at one point.^[15] Eickhoff missed most of the season due to a strained back muscle, followed by a return of the numbness in his fingers, which caused him to be put on the disabled list.^[22] He met with a number of specialists during the summer to evaluate nerve damage that was leading to the numbness, twinges, and tingling in the fingers of his right hand, especially when he threw his curveball; their diagnoses ranged from thoracic outlet syndrome (which was ruled out) to carpal tunnel syndrome, and Eickhoff was given two cortisone shots.^{[23][24][25][26]} In the off-season he signed a one-year contract for $975,000.^[27]

In 2019 with the Phillies he was 3–4 with one save and a 5.71 ERA, and struck out 51 batters in 58.1 innings.^[28] He ended the season on the injured list, first with right biceps tendinitis and then with a blister/laceration on his right middle finger.^[29][30]

San Diego Padres

On December 27, 2019, Eickhoff signed a minor league deal with the San Diego Padres. On August 2, 2020, Eickhoff's contract was selected to the active roster.^[31] The next day he was optioned down and he was outrighted off of the roster on August 24, without making a major league appearance. He elected free agency on August 26, 2020.

Texas Rangers (second stint)

On August 30, 2020, Eickhoff signed a minor league contract with the Texas Rangers.^[32] He did not play in a game with the Rangers organization due to the cancellation of the minor league season because of the COVID-19 pandemic.^[33] He became a free agent on November 2, 2020.

New York Mets

On December 15, 2020, Eickhoff signed a minor league contract with the New York Mets organization.^[34] He was assigned to the Triple-A Syracuse Mets to begin the year. On June 20, Eickhoff was selected to the active roster.^[35] After posting a 4.50 ERA in 2 starts for the Mets, Eickhoff was designated for assignment on June 29.^[36] He was outrighted to Syracuse on July 3.^[37] However, Eickhoff rejected the assignment and elected free agency.^[38] Eickhoff re-signed with the Mets on a minor league contract on July 5.^[38] On July 11, Eickhoff was re-selected to the active roster.^[39] Eickhoff allowed 4 runs in 6.1 innings of work before he was designated for assignment a second time on July 20.^[40] Eickhoff elected free agency for a second time on July 24. Eickhoff again re-signed with the Mets organization on a minor league contract.^[37] On July 27, Eickhoff was added to the team's major league roster for a third time.^[41] That day, Eickhoff took the loss after giving up 10 runs in his start against the Atlanta Braves,^[42] and was designated for assignment yet again the following day. On October 6, 2021, Eickhoff elected free agency.^[43]

Pittsburgh Pirates

On November 30, 2021, Eickhoff signed a minor league contract with the Pittsburgh Pirates.^[44] He was assigned to the Triple-A Indianapolis Indians to begin the season.

On June 22, 2022, Eickhoff was selected to the 40-man and active rosters. In his only appearance, a start against the Chicago Cubs, he was shelled for 10 runs on 10 hits in 4.1 innings of work. He made history as the first Pirate to allow 10 runs in their first start with the squad. He also became the first pitcher to allow 10 runs in back-to-back starts since Chubby Dean of the Philadelphia Athletics in 1940.^[45] Eickhoff was designated for assignment on June 24. He cleared waivers and was sent outright to Triple-A Indianapolis on June 27.^[46] In 28 games (20 starts) for Indianapolis, he posted a 6-7 record and 4.96 ERA with 107 strikeouts in 114.1 innings pitched. He elected free agency on October 6.^[47]

Lexington Counter Clocks

On April 13, 2023, Eickhoff signed with the Lexington Counter Clocks of the Atlantic League of Professional Baseball.^[48] In 9 starts for Lexington, Eickhoff struggled to a 3–4 record and 6.16 ERA with 40 strikeouts in 49+2⁄3 innings pitched.^[49]

Cleveland Guardians

On June 20, 2023, Eickhoff had his contract purchased by the Cleveland Guardians organization.^[50] He elected free agency on November 6. ^[51]