The Rockies promoted Valaika to the major leagues for the first time on September 6, 2016,[6] and made his Major League Baseball debut the same day pinch running for pinch hitterTom Murphy in the bottom of the 8th inning during a game against the San Francisco Giants.[7] He made his first defensive appearance on September 8, 2016, replacing third basemanNolan Arenado in the bottom of the sixth inning, a game where he also got his first plate appearance hitting a double in the bottom of the 8th inning.[8] His first start in the major leagues came against the Los Angeles Dodgers on September 24, 2016.[9]
On October 30, 2019, Valaika was claimed off waivers by the Baltimore Orioles.[11] However, Valaika was designated for assignment by the Orioles on January 10, 2020, to make room for Richard Ureña on their 40-man roster.[12]
On January 16, 2020, Valaika was claimed off waivers by the Arizona Diamondbacks.[13] Valaika was designated for assignment by the Diamondbacks on January 27, following the acquisition of Starling Marte.
On January 30, Valaika was again claimed off waivers by the Baltimore Orioles.[14] He was outrighted to the Norfolk Tides on February 11. On July 23 the Orioles selected his contract to the major league roster.[15] In 2020 for the Orioles, Valaika slashed .277/.315/.475 with 8 home runs and 16 RBI.[16]
On August 5, 2021, after having 193 at-bats and hitting .192 with 4 home runs and 21 RBI, Valaika was designated for assignment by the Orioles.[17] On August 8, Valaika was sent outright to the Triple-A Norfolk Tides. There, he played in 22 games, hitting .225 with 2 home runs and 7 RBI. On September 14, the Orioles re-selected Valaika's contract.[18] Valaika was outrighted off of the 40-man roster on October 23 and granted free agency on October 25.[19]
Atlanta Braves
On March 19, 2022, Valaika signed a minor league contract with the Atlanta Braves.[20] Valaika played in 114 games for the Triple-A Gwinnett Stripers, hitting .242 with 10 home runs, 54 RBI, and two stolen bases.[4] He elected free agency following the season on November 10.
Seattle Mariners
On March 23, 2023, Valaika signed a minor league contract with the Seattle Mariners organization.[21] In 38 games for the Triple–A Tacoma Rainiers, Valaika batted .240 with four home runs and 26 RBI.[4]
Los Angeles Dodgers
On July 4, 2023, Valaika was traded to the Los Angeles Dodgers.[22] In 25 games for the Triple-A Oklahoma City Dodgers, he hit .225/.276/.303 with two home runs and 10 RBI.[4] Valaika elected free agency following the season on November 6.[23]