"I have a lot of regrets over my last game that I pitched," Bassitt told Brodie Brazil of NBC Sports Bay Area. "I think I set the stage to lose the series by the way I did pitch."
Bassitt only started Game 1 of the ALDS, allowing nine hits and three earned runs over four innings in an eventual 10-5 loss. Houston wound up beating Oakland in four games to advance to the championship series.
The Athletics were considered the favorite entering the ALDS after posting a 7-3 regular-season record against the Astros.
The 31-year-old pitcher admitted trying to be too cute against Houston in the division series after facing them three times during the regular season with mixed results.
"I went away from what I usually did and, obviously, they made me pay for it," Bassitt said. "I take a lot of blame personally on the way the series turned out."
Bassitt may shoulder the responsibility for the playoff-series loss, but he was also Oakland's best starter in 2020.
The six-year veteran won five of his 11 starts while posting a career-best 2.29 ERA in 63 innings.
He's projected to be the Athletics' ace in 2021 after finishing eighth in AL Cy Young voting.