Orlando City
Mueller was drafted as the sixth overall pick of the 2018 MLS SuperDraft by Orlando City SC. [7] He made his professional debut on March 3, 2018, in a season-opening 1–1 draw with D.C. United. [8] On April 8, 2018, Mueller scored his first professional goal against Portland Timbers in a 3–2 victory. [9] On April 21, 2018, Mueller scored the fastest goal in Orlando City history when he scored 63 seconds into a match against the San Jose Earthquakes, and later in the match he recorded his first professional assist. [10] Mueller was runner-up for the 2018 MLS Rookie of the Year Award. [11]
On March 2, 2019, Mueller started in his second consecutive season opener, scoring in a 2–2 against New York City FC. He scored his first U.S. Open Cup goal against the same opposition on July 10, 2019, in a 1–1 quarter-final draw before Orlando progressed to their first ever semi-final on penalties. In July 2019, Mueller was part of the Orlando City team alongside Nani and Sebas Méndez that won the 2019 MLS All-Star Skills Challenge, beating teams from the MLS All-Stars and Atlético Madrid to win the $25,000 prize for charity with Mueller notably the only player to successfully complete a scissors kick during the volleys round.
On March 7, 2020, Mueller scored Orlando's first goal of the season in a 2–1 away loss to Colorado Rapids. [12] With the season affected by the coronavirus pandemic, a return to play was achieved through the MLS is Back Tournament. Mueller scored in the opening game as Orlando beat newly formed rivals Inter Miami CF 2–1 before scoring a brace in the following game, a 3–1 victory over New York City FC. [13] He finished the 2020 season as the team's top scorer with a career-high 10 goals.
On July 17, 2021, Mueller appeared as a substitute in 1–1 draw with Toronto FC. It was his 108th appearance for the club in all competitions, tying the record set by Cristian Higuita in 2019. Entering the final year of his contract in 2021, Mueller had been in contract negotiations with Orlando City but informed the club on July 21, 2021, that he had signed a pre-contract agreement with an unnamed European club and that he would be leaving upon the expiry of his contract at the end of the 2021 season. [14] He broke the club appearance record a day later, starting in a 2–1 win over Philadelphia Union.
Hibernian
On July 22, 2021, Scottish Premiership side Hibernian announced they had signed Mueller on a free transfer agreement, which would see him join the club on January 1, 2022. [15] [16]
On January 20, 2022, Mueller made his debut for Hibernian in the side's 1–0 win over Cove Rangers in the Scottish Cup. [17] On February 13, 2022, He scored his first goal for the club in a 3–1 win over Arbroath F.C. in the Scottish Cup. [18] This proved to be the only goal Mueller would score for Hibs, and he was allowed to return to the U.S. in May 2022. [19] Hibs chief executive Ben Kensell said that Mueller had struggled to "adapt to the pace and physicality" of Scottish soccer. [19]
El Salvador 
