Mighty Lucky will remain on a weight-for-age path after his victory in the Lord Mayor's Cup at Doomben on Saturday.

Despite racing three deep for most of the trip, Mighty Lucky, the $4.80 favourite, held off the fast-finishing Pajaro ($14) to win by three quarters of a length with Malice ($17) a half head away third.

Trainer Fred Cowell said Mighty Lucky would back up in next Saturday's weight-for-age Eagle Farm Cup (2200m).

"There's no worries about him backing up. He's the toughest horse ever," Cowell said.

"He's been a wonderful horse to us. He won first-up at Randwick then was unlucky at Hawkesbury and Scone going into this race."

Mighty Lucky will be attempting 2200m for the first time next Saturday but Cowell doesn't think it will be a problem.

"He won the Summer Cup at Randwick over 2000 metres and ran the trip out strongly that day so I think he'll be okay," he said.

"I don't think we've seen the best of him yet and maybe that will come next week when he gets over a bit more ground."

Winning jockey Chris O'Brien praised Mighty Lucky's determination.

"He's been running super races all preparation and a couple of bad barriers haven't helped much but he's so honest and he gives you everything he's got," he said.

"I'm sure he'll go home tonight, lick his bin out and be ready to go again next Saturday. You wouldn't find a tougher horse than him."

Blake Shinn was impressed with the effort of Pajaro to finish second after coming from near last on the home turn.

"The alley was no help to him today but I thought he finished the race off really well," he said.