Sources: Josh Jackson won't work out for Celtics without assurances

— -- The Chicago Bulls and New York Knicks, who are fielding trade offers for their high-profile players, both have shown interest in draft prospect? Josh Jackson, sources tell ESPN's Ramona Shelburne.

The Bulls have the 16th overall pick and the Knicks are slotted at No. 8, so either team likely would have to trade to a higher spot in the first round in order to select Jackson, who widely is projected as a top-five pick.

The 6-foot-10 Jackson worked out last week for the Los Angeles Lakers, who have the No. 2 pick in Thursday's draft. The Boston Celtics, who have the third pick, hoped to have Jackson in for a workout Tuesday, but multiple sources told ESPN's Dave McMenamin that the former Kansas star did not work out for Boston.

A source told ESPN's Chad Ford that Jackson has refused to work out for the Celtics, who have the third pick in Thursday's draft, without an assurance that they are keeping the No. 3 pick and that he is the top player on their board.

ESPN reported Monday night that the Bulls have been engaged in trade talks with the Cleveland Cavaliers, who covet All-Star swingman Jimmy Butler.

The Chicago Tribune reported that the Phoenix Suns, who have the No. 4 pick, could be a potential third team in a Bulls-Cavs trade involving Butler. The Celtics also are regarded as a potential trade suitor for Butler.

The Knicks, meanwhile, have fielded multiple calls in recent days from teams interested in star forward Kristaps Porzingis, ESPN confirmed Tuesday. The New York Daily News reported later Tuesday that the Celtics are one of the teams that reached out to the Knicks.

ESPN's Marc Stein and Ian Begley contributed to this report.