Baggies head coach Clarke signed Argentina international Yacob on a free transfer from Racing Club on the evidence of DVDS presented to him by the then sporting and technical director Dan Ashworth.
His Swansea counterpart Michael Laudrup brought in Michu from Spanish side Rayo Vallecano for £2million and he has been impressive during his first campaign at the Liberty Stadium.
Clarke said: "It's difficult to find a player now that nobody knows about and nobody has got.
"To be fair to Michael Laudrup at Swansea, he obviously has a good grasp of the Spanish market because he's worked there before.
"He would know the capabilities of a player like Michu. It has worked out for him.
"His use of the Spanish market last summer was excellent. They've brought in some really good players from Spain.
"With us, when you spend the amount of money we did on Yacob, and he turns out to be as good a player as he is for the team, that's great.
"Normally a player of the type of Claudio is a players' player, a manager's player or a coaches' player and doesn't really stand out. He just does his job for the team.
"But in doing the job for our team, he has also managed to stand out as being exceptionally good at it. I think he's been tremendous and a big, big bonus for us this season."
Clarke admitted: "I hadn't seen him but either on my first or second day here, I got given a pile of DVDs.
"I had asked for a defensive-type midfield player and Dan (Ashworth) gave me a pile of DVDs with three or four different players.
"I went through them all and thought 'I quite like that one' and we managed to get him in.
"I didn't know him. He was just a name. He didn't play for the last four months of his contract because the club knew he was running it down so it was all on DVDs."
Clarke has seen Yacob start to get to grips with the English language since arriving at the Baggies.
He said: "His English is much-improved, although I'm not sure he understands my Scottish!
"I've had one or two decent conversations with him recently and his character is good.
"He's a little bit like you see on the pitch, quiet, determined. Sometimes I get the feeling he's got more to say but he doesn't quite trust his words yet. I think he will grow into himself."
Clarke has ruled out winger Jerome Thomas moving to Blackburn on loan but is content to allow England Under-21 defender Craig Dawson to remain with Bolton for the rest of the season.
He said: "I had two players unavailable last weekend at Chelsea. One (Goran Popov) was suspended, one (Romelu Lukaku) couldn't play against his parent club. I had Chris Brunt injured and a 16-year-old (Isaiah Brown) on the bench.
"That situation in itself answers the question about Jerome going out. I can't let anyone go. I haven't got a big squad of senior players."