In 1998, Agassi began a rigorous conditioning program and worked his way back up the rankings by playing in Challenger Series tournaments, a circuit for pro players ranked outside the world's top 50.
ɪn nˈaɪntiːnhˈʌndɹɪd nˈaɪnti ˈeɪt, ˈæɡæsi bɪɡˈæn ɐ ɹˈɪɡɚɹəs kəndˈɪʃənɪŋ pɹˈoʊɡɹæm ænd wˈɜːkt hɪz wˈeɪ bˈæk ˌʌp ðə ɹˈæŋkɪŋz baɪ plˈeɪɪŋ ɪn tʃˈælɪndʒɚ sˈɪɹiz tˈʊɹnəmənts, ɐ sˈɜːkɪt fɔːɹ pɹˈoʊ plˈeɪɚz ɹˈæŋkt aʊtsˈaɪd ðə wˈɜːldz tˈɑːp fˈɪfti.