Things did not start particularly well for the visitors as Jack Colback fired Sunderland into a 13th-minute lead as Gus Poyet's Sunderland targeted Premier League survival.
Instead of a West Brom fight-back, Sunderland doubled their lead just after the half-hour mark as Fabio Borini – on loan from Liverpool – netted his sixth league goal of the season.
Victory for Sunderland secured their status as a Premier League club for another year, all but condemning Norwich City to relegation, and Mel was left unimpressed with West Brom's lethargic display.
"I am extremely disappointed," the Spaniard said.
"I would like to apologise to fans who made the long trip. We still have a very important game on Sunday and I hope we play very differently.
"We played with very little intensity in first half. I don't understand what happend. It wasn't good. We were better second half but Sunderland beat us in terms of intensity.
"They have had a really good month and I congratulate them."
West Brom have come very close to relegation this season as they sit just three points ahead of Norwich, although their superior goal difference means Mel's men are almost certainly out of reach.
But the former Real Betis coach is unsure about his future, considering he has just an 18.75 winning percentage from 16 games in charge of West Brom.
"I really don't know," he claimed.
"This is not a decision for me to take.
"I'm not sure. What we really need to try and do is to try and change the image that we are giving against Stoke City."
