Greg Jackson has had a firsthand look at the punching power of Anthony Johnson.

Jackson was in Andrei Arlvoski's corner for a heavyweight fight against Johnson nearly two years ago in Atlantic City. The bout headlined a World Series of Fighting card in March 2013.

Johnson (19-4) dropped Arlovski twice with right hands at the end of the first round. The punches broke Arlovski's jaw in two places, although he managed to finish the three-round fight. Johnson won by decision.

As Jackson prepares UFC light heavyweight champion Jon Jones for a title defense against Johnson, he says he's training him for the hardest-hitting opponent of his career.

"[Daniel] Cormier was knocking people around left and right, too, but as far as raw power, I don't think anybody hits harder in the division than Johnson."

According to Jackson, Jones has not officially started camp for Johnson. The UFC has not announced a date for the fight, but current expectations are that it could headline an event in May.

Jones, 27, recently relocated to Albuquerque, N.M., to dedicate himself full time at Jackson-Winkeljohn MMA. Jackson said Jones has been hitting mitts but won't get fully back into hard training until later this month.

Jackson said he had no preference for Jones between fighting Johnson or Alexander Gustafsson next. The two contenders fought on Jan. 24 in Sweden, with Johnson scoring a quick first-round TKO.

"We've cornered against Johnson before, and he is such an impressive dude," Jackson said. "His punch, good Lord, that thing hits hard. He is going to be a real challenge. That's a loaded gun that can go off at any time.

"I'm good with whoever they put in front of Jon. I don't have any preferences. I'm not like, 'Oh, I wish you could fight so-and-so, because it hardly ever works out that way. Whoever they put in front of me, that's who I have to solve."

In regard to Jones' positive drug test ahead of his title defense against Cormier at UFC 182 on Jan. 3, Jackson said he is not worried about his star pupil's immediate future and believes he has dealt with the matter correctly.

Jones has said he underwent a 24-hour evaluation at a drug-treatment facility shortly after news of the positive drug test and has taken on outpatient therapy. He has denied any serious drug addiction.

"He is definitely a grown man," Jackson said. "I can give my advice to him as a friend and say, 'If you're going to party, make sure you don't repeat your past mistakes,' but I'm not going to follow him around or anything. I'm not a baby-sitter.

"I don't [have any concerns about Jones]. He's doing the right things to get control of the mistakes he made. I'm not worried about him."