The sessions this week at Red Bull Arena — there were also closed-door tests on Tuesday — produced the mixed results that the rules officials and former referees looking on had expected. Some decisions in Wednesday’s session with the youth players were raised and resolved in less than 30 seconds, and without the referee, Ismail Elfath, ever leaving the field.

Others took longer, and sometimes required Elfath to run to the sideline to quickly review several angles of a specific incident on a large electronic tablet. In each case, he had a brief discussion with the video referee upstairs through his headset, and then either affirmed or overturned his decision on the field.

However, in every case Elfath retained the final say on the call. Only the match referee can initiate a formal review of an incident under current protocols, Elleray stressed, and only the video referee can recommend one.

“The referee could say, ‘No, I’ve seen everything clearly; we don’t need to check it on the television,’” Elleray said.

There will be no coaches’ challenges in the replay rules — according to the rules board, players and coaches interviewed strongly opposed them for fear they would be used for gamesmanship or to bring about intentional breaks in play — and for now there is also no time limit on how long a review should take.

The officials also warned fans that they should not expect to see video replay in use anytime soon; the board will not experiment with competitive matches until 2017, although Major League Soccer’s vice president for competition, Todd Durbin, said Wednesday that the league was eager to get started. M.L.S. has been running its own replay experiments for several years.

Even in two days of trials this week, Elleray and others said that they could see progress. Delays with review calls had grown shorter, and the communication between the referees and the video referees had improved, they said.