Claressa Shields explained how she "knew the game I had to play" before defeating Savannah Marshall and "said stuff to get into people's heads."

The American was re-crowned undisputed middleweight champion after a unanimous decision victory over Marshall on Saturday night at The O2, but Shields admitted it was the "hardest fight of her career."

Despite their heated rivalry, which had sparked a war of words, she expressed her admiration for Marshall in the aftermath.

"I knew I had to play the game," Shields explained.

"Some of what I said to her I didn't even mean, but I said it to get to her, and a lot of what I said was true, like how I am not a pushover, a punk, and that even though she punches hard, I am a great fighter."

"In the lead-up, as I said at the start, I never said she was a trash fighter because we both have some of the same background and have been able to observe each other."

"I knew it was going to be a tough fight, but you just have to say things to get into people's heads."

Shields, a three-time undisputed champion, has held world titles at super-welterweight, middleweight, and super-middleweight but has no plans to compete for a light-heavyweight belt in the near future.

"I just want to keep fighting against the best; I'm only 27 years old; I'm not going to retire until I'm probably 35 or something," she added.

"Whoever the best is.... if there are any up-and-coming girls coming up to 160[lbs] who think they can beat me, I will fight them, I will fight my mandatorys, and I really just want to make history.

"I'm not going to 175 pounds for a year or two because those girls are fast, and we need to build some power and muscle for them.

"I have all the skill in the world, but because I am a logical fighter, it will take me a year or two to master.

"147 pounds, the girls can get smoked, 154 pounds, the girls can get smoked, 160 pounds, the girls can get smoked, and 168 pounds, Franchon Cruz, my sister, will fight Christina Hammer.

"If they give us a big check, we'll fight, but if they don't give us a big check, I don't think I'll do it."

Claressa Shields is the GWOAT, according to Marshall.

Shields' post-fight respect was matched by Marshall, who admitted following their thrilling fight that her opponent was unquestionably the greatest women's boxer of all time.

"Claressa is a brilliant fighter - not as quick as I expected! She has definitely earned the title of Greatest Woman of All Time," Marshall told All Sports.

"I want to thank everyone who purchased a ticket; I truly appreciate it."

"It's incredible that two women sold out The O2." It's incredible, and I want to thank everyone from the bottom of my heart."