Riquna Williams scored a game-high 26 points for the Shock in a 86-59 win over the Seattle Storm on Wednesday.
Diggins, the third overall pick in the draft, was out with an ankle injury she suffered in Saturday's loss to Minnesota.
Rookie Angel Goodrich stepped into the starting lineup in place of Diggins and scored a season-high 14 points for the Shock (4-13).
"Obviously, it was a big role to step into," Goodrich said. "I just wanted to go out and be aggressive."
The Shock begin a four-game homestand on Friday, but Shock coach Gary Kloppenburg said he did not know whether Diggins will be available.
"It's day to day with her, with her ankle," he said Wednesday.
Camille Little led the Storm with 11 points. Tina Thompson, with 10 points, was the only other player in double figures for Seattle (6-9).
Glory Johnson added 15 points for Tulsa, which had four players in double figures.
Three of Tulsa's four wins this season have come against the Storm.
"We just seem to do really well against them," Kloppenburg said. "We really came out with a lot of energy, and when your shots are falling, it really energizes your defense."
The Shock never trailed after jumping out to a 10-2 lead in the first 4½ minutes and building a 19-point advantage at halftime. Liz Cambage helped the Shock to the early lead, scoring seven of her 13 points.
The Storm's five starters combined to score eight points on 3-for-15 shooting in the first half.
Williams scored 15 of her game-high 26 points after halftime. She has scored 20 or more points in three of the Shock's past four games.
"She's a dynamic player, an explosive player off the bench," Kloppenburg said. "I've been bringing her off the bench, and she really seems to thrive in that role."
Said Williams: "I love coming off the bench. When you're starting, there's too much pressure."
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