The world-traveling Blackley gave up three runs in the first on three hits, then settled down to hold the Angels to just two hits over his final two innings of an Oakland Athletics split squad's 13-13 tie with Los Angeles on Saturday.
Weaver, the Angels' opening day starter, struggled even more at the start, allowing eight runs and three homers in two innings.
"I don't have the luxury of giving up an eight-spot and still be the opening day starter," Blackley said.
Blackley, who has pitched for three major league clubs, a professional team in Korea and one in his native Australia, gave up three runs on three hits in the first inning and committed a throwing error.
He settled down after that.
"There was more intensity behind each pitch, more conviction," said Blackley after his fifth appearance of the spring and second start.
He added that he was getting more into a rhythm.
"It was good, kind of how I felt last year," said Blackley, who was 6-4 in 24 games (15 starts) for Oakland after being claimed off waivers from Bay area neighbor San Francisco Giants on May 15.
He has now been with both clubs twice in his career.
Blackley's highlight was retiring Angels designated hitter Albert Pujols twice, the second time on a strikeout. He said he thought Pujols was expecting a curveball after he threw him several fastballs, but he came back with a two-seamer.
"He's one of the great hitters on the planet," said Blackley, who had faced Pujols a handful of times last season. "It must be tough being him, having that target, having pitchers come at him every time."
Weaver gave a three-run homer to Josh Reddick in the first inning and two-run shots to Luke Montz and Yoenis Cespedes in the second.
Is Weaver experiencing a "dead arm," which many pitchers have at this point of the spring?
"It was a rough outing. Whatever term you want to put on it, it just wasn't there for him," Angels manager Mike Scioscia said. "I think he felt like he didn't have a good release point."
It was disappointing, Scioscia said, to get only two innings out of a guy who was targeted to throw about 75 pitches in five innings.
NOTES: A's LHP Brett Anderson, who left his previous start early with a straight right trapezius muscle (neck area), pitched five innings in a minor league game in nearby Mesa, Ariz. Oakland's opening day starter said he was fine after throwing 62 pitches in five innings and gave up five hits, walked four and struck out three. ... A's closer Grant Balfour, coming back after minor knee surgery, is due to make his spring debut on Monday. ... Angels 3B Alberto Callaspo batted cleanup and had three hits (two doubles) and drove in a run. ... LF Mike singled, drove in a run, scored one and walked while batting leadoff.