She feared she was out too fast.

“So, she backed off and lost the pace, but should have kept her speed up,” said her coach, Mason Rebarchek, in assessing Shereen’s run.

“It didn’t go her way, but she knows the tactical error she made in the middle of the race was the difference,” Rebarchek said.

“It was a great experience and she has confidence now going into the Commonwealth Games.”

Shereen, a wild card entry in her maiden worlds, finished seventh out of the eight runners, two of whom are among the top ten 400m runners in the world.

Ranked 229 in the world, she clocked 53.56s, almost a second slower than her personal best of 52.68.

Shereen had been expected to break the 29-year-old national 400m record of 52.56s set by Rabia Abdul Salam after her smashing runs in collegiate competitions in the US.

Poland’s Anna Kielbasinska posted 50.63s to win the heat ahead of Jamaica’s Olympic finalist Candice McLeod (50.76s) and Victoria Ohuruogu of Britain (51.07s).

Shereen said: “The race didn’t go as well as I wanted to as I made a tactical mistake in the back stretch of the 400m.

“I’m disappointed with myself but it’s important for me to keep my chin up and shift my mind positively to the Commonwealth Games.”

She said she was thankful to the National Sports Council and the Malaysia Athletics Federation for giving her the opportunity to compete in the championships.

Her Olympian mother, Josephine Mary, who is at Oregon22 as the team manager, hoped Shereen would bounce back stronger.

With Shereen’s exit, Malaysia’s campaign in Oregon has ended.

On July 15, high jumper Nauraj Singh Randhawa suffered an ankle injury and finished last with “no jumps”.