Jokanovic arrived in 2014, the fourth manager in two months, with the club struggling in the Championship.
But under the Serb's guidance, the Hornets won promotion in 2015 and have remained in the top-flight ever since.
"That season, we got off to a flyer under (Giuseppe) Sannino and were second in the table after only six matches, winning five of them and losing only once," Angella said.
"But then Sannino's sudden and unexplained decision to walk away left us players deflated and the whole club in a mayhem for a while. To top it all, Sannino did not disclose any reasons for terminating his contract and walking away.
"It was a difficult year because we changed four different managers. We had Sannino and two other managers along the way, who only stayed for a very brief period of time. One of them stepped down because he was taken ill (Oscar Garcia) and Billy McKinlay. I don't even know why the club appointed and relieved him of his duties so quickly.
"To compound matters, Watford also had to deal with a growing list of injuries at that time. Troy Deeney, Almen Abdi and I suffered injury setbacks at the same time, which was a big blow for the entire club. All three of us spent a month and a half on the sidelines, which did not help Watford's case, with the club further slipping down the table.
"Then Jokanovic took over and did a great job in bringing stability and serenity to the club. He really steadied the ship. His man-management skills and know-how got us back on track. This eventually culminated in Premier League promotion."
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