The midfielder's father and agent has confirmed that the Premier League champions held talks with the Spain Under-20 star but he ultimately opted to join Bayern Munich
The Red Devils offered the Spain Under-20 international a 140,000 euro-a-week deal to move to Old Trafford, with the 22-year-old having agreed terms in principle.
Thiago's head was soon turned, however, with the prospect of reuniting with Guardiola in Germany, which prompted a rethink that saw him move to the Champions League holder.
Mazinho has revealed that his son did almost decide to join David Moyes' side, however.
"Thiago was very close to signing with Manchester United," he told La Xarxa. "They had talks. But they couldn't find an agreement."
Thiago scored his first goal for Bayern in the 5-1 Telekom Cup victory over Borussia Monchengladbach on Sunday and started against Barca in a friendly on Wednesday.