[1] Niemann, who stands 6 feet 9 inches (2.06 m), was the fourth starter for Rice University in his freshman season of 2002, usually starting midweek non-conference games.

He finished the season 17–0 with a 1.70 ERA and 156 strikeouts, being named Western Athletic Conference Pitcher of the Year, a consensus first-team all-American, and a finalist for the Rotary Smith Award in helping Rice to its first national championship.

Flanked in the rotation by starting pitchers Andy Sonnanstine and Mitch Talbot during the Southern League playoffs, Niemann helped lead the Biscuits to the 2006 championship.

Niemann made his major league debut on April 13, 2008, against the Baltimore Orioles, pitching 6 innings en route to his first career win.

The Tampa Bay Chapter of the Baseball Writers' Association of America named him the Rookie of the Year for the Rays for the 2009 season in a unanimous decision by the voters.