The Boston Celtics and Cleveland Cavaliers pulled off the biggest trade of the summer after agreeing a deal to swap All-Star point guards Kyrie Irving and Isaiah Thomas. The Cavs also received Jae Crowder, Ante Zizic and the Brooklyn Nets' 2018 unprotected first-round pick as part of the deal.The trade shocked the NBA world and has been a major talking point throughout the week as it's extremely rare to see two rival teams swap star players. However, there could now potentially be a major twist that could cause problems to the completion of the trade.According to ESPN's Adrian Wojnarowski, Thomas underwent a physical examination in Cleveland on Friday and there is real uncertainty over his hip injury. Per Wojnarowski, Cavaliers officials are still evaluating the results and considering possible ramifications to the trade. One source involved in the process told the ESPN insider, "It's a very sensitive situation."

The two-time All-Star injured his hip against the Cavs in the Eastern Conference Finals and has not undergone surgery.

Boston's doctors decided that surgery wasn't required and instead told the player to undergo a summer of rest and rehabilitation.

Per ESPN, Thomas still hasn't started running again during his rehab process and it's now becoming a huge concern for the Cavaliers.

Celtics general manager Danny Ainge admitted on Tuesday that IT's hip injury played "some" part in the team's decision to trade him and it's now clear to see why.  

The worst case scenario could see the Wine and Gold void the deal, but according to Wojnarowski, the Cavaliers may potentially push Boston to sweeten it and add another draft pick, but no conversations have taken place yet. 

The Ohio-based franchise are still evaluating the medical information and no final decision has been made, per league sources.

All players must pass a medical or a trade can be voided and the Cavs will now be left in a tricky predicament as Isaiah's hip injury looks to be worse than initially feared. 

Cleveland is due to begin its training camp next month with the regular season campaign tipping off against Boston on 17 October. 

The likelihood of seeing Thomas line up for the Cavaliers against his former employers is looking increasingly unlikely.

At this stage, the most important thing is to get the dynamic point guard back to full health and playing at a high level again. 

But there are sure to be more developments on this story in the coming weeks.