Johansson won his first ATP singles title in 2004 when he overcame
Nicolas Kiefer in the
Memphis final. In
2005 he won another two titles (
Adelaide and
Marseille).
He caused a huge upset at the 2004
US Open when he beat defending champion
Andy Roddick in five sets in the quarterfinals. An unusual aspect of the match was that Roddick won 24 points more than Johansson but was defeated nonetheless. Johansson subsequently lost his semifinal against
Lleyton Hewitt.
Johansson underwent shoulder surgery in July 2005, forcing him to stop playing the rest of the year. In 2006 he added physical rehabilitation and development practice with coach
Agne Bergvall together with Swedish track and field stars
Carolina Klüft, Susanna and
Jenny Kallur. In February 2006, he played in the SAP Open in San Jose but sustained another injury. He was then forced to skip tournaments in Indian Wells and Miami until beginning a second comeback in July 2006 by playing Challenger and Futures tournaments.
In
October 2006, Johansson made a triumphant return to the ATP Tour in the Stockholm Open. As a wildcard, he defeated
Davide Sanguinetti in the first round, and stunned top seed and world number two
Rafael Nadal in straight sets in the second round. In that match, Johansson fired 17 aces, and announced his return to the top of the game, calling it his "greatest win ever." Johansson made it to the semifinals of the tournament before losing to fifth-seeded
Jarkko Nieminen in three sets.
In his next tournament, the
Madrid Masters, Johansson pulled off another upset in the second round, defeating fifth-seeded
Nikolay Davydenko in three sets. He was forced, however, to withdraw from his next match due to a throat infection.