McNally started the 1973 season with a shutout of the Brewers on April 6. Six days later, he pitched shutout ball for innings, limiting Detroit to three hits in the Orioles' 1–0 win in 10 innings. On May 10, he threw 10 innings against Oakland, but Joe Rudi's RBI double in the 10th provided the winning margin in Oakland's 4–3 victory. He gave up 10 hits to the Yankees on June 27 but no runs in the Orioles' 4–0 victory. On September 1, he shut out the Yankees again as the Orioles prevailed 1–0. McNally's record was 9–12 after his start on August 3. He brought it to 17–16, moving his winning percentage over .500 with a victory over the Brewers on September 23, but he lost his last game of the year six days later to finish the season at 17–17. In 38 starts, he had a 3.21 ERA, 87 strikeouts, 81 walks, and 247 hits allowed in 266 innings. His 17 losses tied with Bert Blyleven and Rudy May for fifth in the AL, but his 3.21 ERA ranked ninth in the league.