Oakland Athletics manager Bob Melvin reflected on a "stressful" first use of MLB's new extra-inning rule, even though his team enjoyed a dramatic Opening Day win.

With the start of the 2020 season delayed due to the coronavirus pandemic, new measures have been brought in to ease the load on players, including a reduced schedule prior to an extended playoffs.

In an apparent bid to prevent long games, the league also introduced a rule where a runner is placed at second base at the start of each half-inning after the ninth.

And with the A's and the Los Angeles Angels tied at 3-3 through nine innings, the regulation made its eye-catching MLB debut on Friday.

Shohei Ohtani, of the Angels, was the first man stationed at second - having been last out in the ninth - only for the A's to quickly extinguish Los Angeles' advantage as Burch Smith worked a scoreless inning.

It was Smith's debut following a trade from the San Francisco Giants, and Melvin was delighted with the way he dealt with the unprecedented circumstances.

"It's stressful," the manager said. "You've got a man on second and you didn't do anything to put him there.

"It's your first big-league game with us and you've got very little room for error. He ended up doing a great job."

Oakland then loaded the bases in the bottom of the 10th for Matt Olson to hit a walk-off grand slam and clinch a brilliant 7-3 win.

Hello yes @mlb we can confirm the new extra inning rules are VERY good #RootedInOakland pic.twitter.com/soVyXeS6Y3
— Oakland A's (@Athletics) July 25, 2020

Olson's walk-off grand slam was the first on Opening Day since the Seattle Mariners' Jim Presley in 1986.

Melvin said of his game-winner: "He's got a flair for the dramatic. He had a good idea of what he was looking for up there, and he got it.

"He was just trying to get the ball in the air, and he did more than that.

"We've seen 'Oly' walk off against some pretty good left-handers. We always feel good about him in those situations."

Two-time Gold Glove first baseman Olson had also had a hand in catching out Ohtani in the extra inning, firing the ball to Matt Chapman at third for the rundown in a move the pair had discussed previously.

"Those two have been talking about that play for a long time," Melvin said. "It didn't surprise me. Two terrific defenders made a great play. That was a game-saver."

Olson added: "We talk about it a bunch. I feel like [Chapman] is athletic enough to get over to the bag, and I have a good enough arm to get it across for an out.

"Going forward, this is something that's going to be open to do."