An injury has forced UFC flyweight champion Demetrious Johnson out of his scheduled title defense on April 13, according to a report by Ariel Helwani on Tuesday’s UFC Tonight. Johnson was expected to fight John Moraga on the date, at The Ultimate Fighter 17 Finale in Las Vegas.It would have been a quick turnaround for Johnson, who went five rounds in a unanimous decision win over John Dodson at UFC on FOX 6 on Jan. 26. That win marked his first successful title defense after capturing the belt last September.He had hoped to gun for his second defense against Moraga, a 28-year-old Arizona-based fighter who is 13-1 and riding a seven-fight win streak. Moraga has two consecutive finish wins in his UFC run, with a submission over Chris Cariaso and a knockout of Ulysses Gomez.A hunt is on for a replacement for the scuttled main event. Other matches scheduled for the show include a women’s match between Miesha Tate and Cat Zingano, and a heavyweight fight pitting Gabriel Gonzaga vs. Travis Browne.