He played a handful of games for them in 1968, then was selected in the 1968 Major League Baseball expansion draft by the Royals, becoming an everyday player over the next two years with the fledgling franchise.
Traded to the Orioles after the 1976 season, he received significant playing time in left field in 1977 and 1978, then served as a bench player the next two years.
With a career-high .536 slugging percentage in 1979, Kelly helped the Orioles reach the MLB playoffs, appearing in the World Series, which Baltimore lost to the Pittsburgh Pirates in seven games.
His parents had originally lived in South Carolina, but they had moved to the Nicetown neighborhood of northern Philadelphia in the 1920s, when Orvin was hired by a steel company.
After allowing home runs, he would often display a bad attitude, but the reprimands of coach Pete Lorenc eventually helped him overcome the habit.
[4][6] Kelly expected a promotion to the Class AA Charlotte Hornets of the Southern League in 1966; thus, he was very disappointed when he found out the Twins planned to send him back to Wilson.
[4] In 1967, Kelly moved up to Class AAA, spending most of the year with the Denver Bears of the Pacific Coast League (PCL).
On September 23, he hit his first major league home run, coming against Clyde Wright in a 3–0 victory over the California Angels.
[1] While Kelly was in Venezuela, the Kansas City Royals selected him in the fourth round of the 1968 Major League Baseball expansion draft.
[12][13][14] On September 11, against the Oakland Athletics, his single with two outs in the eighth inning spoiled a no hitter by Vida Blue, who went on to complete one 10 days later.
[3] Kelly was traded along with Don O'Riley from the Royals to the Chicago White Sox for Matias and Gail Hopkins on October 13, 1970.
[15] Before he played a game for the White Sox, Kelly spent the 1970–71 offseason in Venezuela with the Tiburones de La Guaira.
[1] Kelly was less successful in spring training with the White Sox, as he ran into a fence and hurt his right knee, struggled to hit, and was sent to the minor leagues to begin the season.
[3] After the season, he played for the Tiburones again, hitting no home runs but batting .400 as La Guira reached the final round of the playoffs.
"It's a good thing my boy didn't leave Kelly out of the lineup," manager Chuck Tanner quipped with reporters afterwards.
[16][17] Adept at base-stealing, Kelly's "small ball" contributions helped the White Sox finished second place in the American League (AL) West Division, behind Oakland.
[3] After the season, Kelly played in the Venezuelan leagues for the last time, batting .296 with two home runs in 35 games as the Tiburones reached the playoffs.
"[1] On the strength of his hot start, Kelly was selected to the AL All-Star team for the only time in his career, chosen by manager Dick Williams.
[1] With the White Sox trailing Oakland 3–2 in the first game of the season on April 8, and the tying run on second base, Kelly had a pinch-hit single against Rollie Fingers.
[21] The transaction was based on a perceived surplus of left-handed hitters and the lack of quality catchers, the latter of which was not solved as Duncan was released the following March without ever having played a game for the White Sox.
"[2][22] On June 3, Kelly was part of what sportswriter Fred Rothenberg called "one of the strangest triple plays in baseball history."
With the bases loaded for the Royals in the ninth inning, and Kansas City down 7–5, John Wathan hit a fly ball to right field that Kelly caught for the first out.
[3] Mora returned to Mexico for the 1979 season, and Gary Roenicke became the primary left fielder for the Orioles, limiting Kelly to a bench role.
In the 10th inning of a game against the Red Sox on May 23, Kelly had a pinch-hit, walkoff home run against Bob Stanley to give Baltimore a 5–2 victory.
Facing Dave Heaverlo with the bases loaded, Kelly hit a grand slam, earning curtain calls twice from the ecstatic fans at Memorial Stadium as Baltimore won 7–4.
[24] He hit a three-run home run against John Montague in Game 4, putting the Orioles up 8–0 in a win that sent them to the World Series against the Pittsburgh Pirates.
[1] Though raised in a Baptist household, Kelly moved on to a lifestyle of "liquor, drugs, [and] women" after his major league career began.
He and White Sox teammate Paul Casanova opened the La Pelota nightclub in Caracas, Venezuela, during the 1971–72 offseason.
Scott McGregor, Tippy Martinez, Doug DeCinces, Kiko Garcia, and Ken Singleton became Christians as a result of Kelly's influence.
Kelly's service was not just confined to Maryland; he assisted in charity work as the executive director of the Cleveland-based Christian Family Outreach.