By Keith Idec

Freddie Roach knows exactly what Mercito Gesta is up against on Saturday night.

Roach trained Jorge Linares for part of his career, including his last loss nearly six years ago. What Roach learned about Linares during that second-round technical knockout defeat to Sergio Thompson and at other points is that Gesta, a big underdog, can win their fight for Linares’ WBA lightweight title.

HBO will televise Linares-Gesta as the opener of a “Boxing After Dark” doubleheader from The Forum in Inglewood, California (10:30 p.m. ET).

“It’s a very, very tough fight,” Roach told BoxingScene.com. “[Linares] is a very good fighter. I worked with him before. But Gesta could take his heart. The thing is, he’s getting older and so forth, and once he gets caught, he falls apart. If you frustrate him, he falls apart. If things don’t go his way, he can be a little bit of a baby. At this point in his career, I think we have a very good shot to win that fight.”

Venezuela’s Linares (43-3, 27 KOs) has won 12 straight fights since Thompson dropped him in the second round and Linares couldn’t continue due to a cut on his left eyelid in March 2012.

His loss to Thompson was Linares’ second straight TKO defeat. In his previous fight, Mexico’s Antonio DeMarco stopped him in the 11th round.

The 32-year-old Linares has since re-emerged as an elite lightweight.

“Linares is a great fighter,” Roach said. “He’s had a great career and so forth. For anyone to get a win over him, that’s a great, great achievement, because he is a very good fighter.”

 That said, Roach is confident Gesta (30-1-2, 17 KOs) can pull off an upset in what has been criticized as a mismatch. He believes the Filipino southpaw will fare much better than he did during his first title shot – a lopsided loss to former IBF lightweight champ Miguel Vazquez in their 12-rounder five years ago.

“I know they gave Peter Nelson a bunch of sh*t about this fight,” Roach said, referring to the HBO executive that approved Linares-Gesta. “I told him, ‘We’re gonna save the day for you, because we’re gonna win this fight.’ ”

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.