1995.
Mariano Rivera pitched 67 innings in his rookie season of 1995.
MLB players lose their rookie status at the beginning of the season after having pitched 50 total innings, having 130 total at bats, or having been on an MLB team's roster for 45 days.
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Mariano Rivera first entered the MLB in 1995 after playing in the Yankees minor league affiliates for five years. The 12 time American League All Star has spent his entire career with the Yankees.