The 22-year old midfielder has failed to make an impact at Sporting with the club sending him on loan over the past three years and it looks like he could be on his way to Ewood Park along with Galatasaray's Colin Kazim-Richards who will join on a season-long loan.
"We are just waiting on the final paperwork for Diogo and we are hopeful we can get something done for Colin very soon too," said Kean in the Lancashire Evening Telegraph.
"I think we would be there then, after signing another striker, providing we can keep everyone.
"When you look at the squad and you see the depth, we are very close if we can get these striker positions filled. Colin would count as one of them."