The following season, Christopher was part of an optimistic 1945 Athletics team, so much so that coach Earle Mack felt that Christopher, Black, Newsom and Jesse Flores were the best quartet of starting pitchers in the league. He spent most of spring training holding out for a new contract, which was eventually agreed on in the middle of March. He missed the first couple weeks of the season due to injury, and won his season debut on April 18, a 12-inning shutout against the Senators. He followed that up with a victory over the Boston Red Sox, allowing only one earned run in his first 21 innings of the season. In mid-June, Christopher had won ten games, which not only led the league, but was more than the seven the rest of the Athletics pitching staff had combined. On July 21, Christopher was part of a 24-inning game against the Tigers that ended in a 1–1 tie; he went 13 innings in the game while Joe Berry pitched the other 11. Although Christopher had a strong start to the season, he struggled during the second half. He lost seven straight games over a two-month period before winning another on August 19 against the Tigers. He finished the year with a 13–13 record and a 3.17 ERA. He was selected to the American League All-Star team, however the game was canceled as a result of World War II.