Washington - Tendai Mtawarira, who helped South Africa capture the 2019 World Cup title, and two former New Zealand All-Blacks highlight new stars for Saturday's start of the third season for Major League Rugby.

Mtawarira, a 34-year-old loosehead prop better known as "The Beast," joined Old Glory DC, one of three expansion teams that boosts the North American rugby union group to 12 clubs.

"I really want to thank the whole Old Glory organisation for making this happen," Mtawarira said.

"I can't wait to make an impact on and off the field and help to contribute to making Old Glory the best team in this league."

Ma'a Nonu, a 37-year-old centre who helped New Zealand capture the 2011 and 2015 World Cup crowns, has joined the San Diego Legion.

"Ma'a is a huge addition for us," Legion coach Rob Hoadley said.

"It's undeniable that he will have a major impact on the MLR this season. He is a world class player who has proven himself to be one of the greats of the game."

Rene Ranger, a 33-year-old centre who made six appearances for the All-Blacks from 2010 to 2013, will play for the Colorado Raptors.

Add French centre Mathieu Bastareaud, who joined Rugby United New York last June, and its clear the league has boosted its talent level as it adds Old Glory from Washington, Rugby ATL (Atlanta) and the New England Freejacks to the line-up.

The Freejacks feature 34-year-old Japanese tighthead prop Kensuke Hatakeyama, whose 78 appearances for his homeland include the 2011 and 2015 World Cups, where he started in Japan's upset of South Africa.

The 2020 campaign kicks off Saturday with Colorado at Houston and New Orleans hosting Old Glory in Mtawarira's debut.

"Not only am I excited about what Tendai brings to the pitch, but also what he brings to our environment," Old Glory coach Andrew Douglas said.

"To have a guy who has played 117 Test matches yet is still so hard working and humble can only be beneficial for us.

"The signing takes the league to another level."

Two-time defending champion Seattle will open against San Diego on Sunday.