Simultaneously, he compiled a 25-1 record playing American Legion Baseball, helping Post 6 win the 1972 Indiana state championship.
[2] In his first season of professional baseball with the Spartanburg Phillies, Underwood went 13-6 record with a Western Carolinas League leading 2.10 ERA and 187 strikeouts.
After striking out the first batter he faced (Dan Driessen), Cesar Geronimo followed with a single and Dave Concepción followed with a double.
He intentionally walked George Foster to load the bases for opposing pitcher Don Gullett.
[5] On May 13, facing the Cincinnati Reds for the first time since his major league debut, Underwood pitched his second career shutout.
[6] For the season, Underwood went 14-13 with a 4.14 ERA and 123 strikeouts to be named the left-handed pitcher on the Topps All-Star Rookie Team.
Underwood walked the first batter he faced, Geronimo; Ed Armbrister successfully bunted the runners over.
In his first start as a Cardinal against the Los Angeles Dodgers, he was trailing 2-1 when he exited the game in the fourth with the bases loaded.
Clay Carroll allowed all three inherited runners to score, giving Underwood five earned runs in 3.1 innings pitched.
Manager Roy Hartsfield made the unusual decision to move the staff's de facto ace, Jesse Jefferson, into the bullpen for 1979.
By default, Underwood became the "ace," and was given the opening day assignment against the reigning American League West champion Kansas City Royals.
After walking clean-up hitter Al Cowens, Underwood induced a double play ball from the next batter Hal McRae.
He recorded his first out of the inning against future Hall of Famer George Brett, but also walked two batters and allowed a base hit to bring the score to 4-0 with Amos Otis coming to the plate.
Over eight innings, Underwood had walked three and allowed five hits as he stepped to the mound in the ninth with the Jays holding onto a 4-3 lead.
Paul Molitor hit a ground ball back to Underwood, who threw it home for the force out at the plate.
On November 1, 1979, the New York Yankees traded post season hero Chris Chambliss and young prospects Dámaso García and Paul Mirabella to the Jays for Underwood, catcher Rick Cerone and minor league outfielder Ted Wilborn.
He began his Yankee career in the bullpen, going 1-2 with a save and a 3.10 ERA before becoming one of four left handers in the starting rotation.
His pattern of bad first starts in which he can't escape the second inning continued against the Baltimore Orioles on April 30,[25] however, he followed that up with six victories in a row.
He lost four of his next five, including the worst start of his career against the Texas Rangers (5 batters faced, no outs recorded, 5 earned runs).
Underwood pitched two scoreless innings, but so did Royals closer Dan Quisenberry, to complete the three game sweep.
[28] Underwood had a 1–4 record with a 4.41 ERA when he was traded along with Jim Spencer from the Yankees to the Oakland Athletics for Dave Revering, Mike Patterson and minor-league left-handed pitcher Chuck Dougherty on May 20, 1981.
One of which was a four hit 5-1 victory over the Blue Jays in which he struck out a career high ten, including the last four batters he faced.
Underwood faced just one batter in the 1981 American League Division Series with the Royals, striking out Willie Aikens.
[31] The A's swept the Royals in the ALDS to face Underwood's former team, the Yankees, in the 1981 American League Championship Series.
He had also received a three-year offer from the Cleveland Indians but sacrificed security for an opportunity to play with the defending World Series champions.