He played in Major League Baseball (MLB) for the Minnesota Twins, Baltimore Orioles, and Chicago Cubs.

Duensing went to Millard South High School in Omaha, Nebraska, where he earned second-team All-State honors in both his junior and senior years.

Duensing was a college teammate of New York Yankees pitcher Joba Chamberlain and Kansas City Royals left fielder Alex Gordon at the University of Nebraska.

After sitting 2004 out as a medical redshirt having Tommy John surgery, Duensing had a breakout season going 8–0 in 2005 with a 2.60 ERA in 21 appearances.

He threw 15 consecutive shutout innings in the Big 12 baseball tournament and helped the Huskers reach the 2005 College World Series 50 miles away.

In 2006, he went 5–10 in 28 games with a 3.49 ERA with 3 teams, the AA New Britain Rock Cats, A Fort Myers Miracle and A Beloit Snappers.

He was then promoted to the Triple-A Rochester Red Wings, where he went 11–5 with 3 complete games, 3.24 ERA and 86 strikeouts for the rest of the season.

[2] Duensing was 5–11 with a 4.32 ERA and 76 strikeouts in 23 starts with the Red Wings in 2008 before ending his season in order to represent the United States at the 2008 Olympics.

[3] He posted Brian's Baseball Blog from Beijing to give fans personal insight to the games from a player's perspective.

[4] In his only appearance, on August 16, Duensing pitched 3.1 scoreless innings in relief to earn the win for team USA against Canada.

[8] The next day he made his second appearance of the season, relieving 32⁄3 innings, allowing one run on one hit while walking one and striking out two against the Detroit Tigers.

[9] On July 29, Duensing made his first major league start, against the Chicago White Sox, filling in for Francisco Liriano, who was scratched with inflammation in his left forearm.

While his season did have some bright moments, including his July shutout against the Tampa Bay Rays, Duensing's pitching did not live up to the potential that he had shown in the later parts of 2010.

Duensing was placed on the injured list on June 22 with left elbow inflammation, and rehabbed the injury with the Double-A Bowie Baysox and the rookie-level GCL Orioles before being activated on September 5.