While Munguia didn't knock Smith out, he easily won the 154-pound fight by scores of 116-111, 119-110 and 119-108.
Joshua, the reigning WBA, IBF and WBO champion, faces mandatory challenger Povetkin at Wembley on September 22.
Pacquiao lost a unanimous points decision to the unbeaten Mayweather (50-0) in one of the richest fights in boxing history in 2015.
The Filipino legend showed his speed, agility, lightning quick movements and punching power from the first bell to overwhelm Argentine Lucas Matthysse.
The 39-year-old knocked out Argentine Lucas Matthysse to be crowned WBA welterweight champion.
The Filipino is challenging Matthysse for the WBA welterweight belt at the Axiata Arena on Sunday.
Pacquiao, 39, faced calls to retire from friends, family and even his Hall of Fame trainer Freddie Roach when he lost the WBO belt to Australian Jeff Horn a year ago.
Argentina's Matthysse will take on the Filipino boxing legend in the WBA title clash on Sunday.
The 28-year-old Briton won his first world title in 2016 and has made five defences, taking his record to 21-0 with 20 knockouts.
The two fighters had been due to fight each other in Las Vegas in May before the middleweight bout was cancelled after Alvarez failed a drug test.
The 37-year-old won 28 of his 32 bouts including 26 knockouts.
Fury only got going in the fourth round and his brief exhibition of power convinced Seferi's corner to pull out the Switzerland-based Albanian before the start of the fifth round.
Santa Cruz improved to 34-1-1 with 19 career knockouts by winning on all three judges scorecards, 115-113, 116-112, 117-111 at the Staples Center arena.
Shelly Finkel, one of Wilder's co-managers, told ESPN that negotiations with Joshua's camp are ongoing, with the possibility of a fight held towards the end of the year.