At 5:12 of the first period in the Penguins/Lightning game, Pittsburgh requested a Coach's Challenge to review whether Tampa Bay was off-side before the puck entered the Pittsburgh net.
After reviewing all available replays and consulting with NHL Hockey Operations staff, the Linesman determined that Tampa Bay's Jonathan Drouin was off-side prior to the goal. According to Rule 78.7, "The standard for overturning the call in the event of a 'GOAL' call on the ice is that the Linesman, after reviewing any and all available replays and consulting with the Toronto Video Room, determines that one or more Players on the attacking team preceded the puck into the attacking zone prior to the goal being scored and that, as a result, the play should have been stopped for an "Off-side" infraction; where this standard is met, the goal will be disallowed."

Therefore the original call is overturned - no goal Tampa Bay Lightning.
The clock is re-set to show 14:53 (5:07 elapsed time), when the off-side infraction occurred.
Since the Coach's Challenge resulted in the original call being overturned, the Pittsburgh Penguins retain their time-out.
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Coach's Challenge
1. A team may only request a Coach's Challenge to review the following scenarios:
a) "Off-Side" Play Leading to a Goal
A play that results in a "GOAL" call on the ice where the defending team asserts that the play should have been stopped by reason of an "Off-Side" infraction by the attacking team.
b) Scoring Plays Involving Potential "Interference on the Goalkeeper"
(i) A play that results in a "GOAL" call on the ice where the defending team asserts that the goal should have been disallowed due to "Interference on the Goalkeeper," as described in Rules 69.1, 69.3 and 69.4; or
(ii) A play that results in a "NO GOAL" call on the ice despite the puck having entered the net, where the on-ice Officials have determined that the attacking team was guilty of "Interference on the Goalkeeper" but where the attacking team asserts: (i) there was no actual contact of any kind initiated by an attacking Player with the goalkeeper; or (ii) the attacking Player was pushed, shoved, or fouled by a defending Player causing the attacking Player to come into contact with the goalkeeper; or (iii) the attacking Player's positioning within the goal crease did not impair the goalkeeper's ability to defend his goal and, in fact, had no discernible impact on the play.
2. A team may only request a Coach's Challenge if they have their time-out available and the Coach's Challenge must be effectively initiated prior to the resumption of play.
3. If the Coach's Challenge does not result in the original call on the ice being overturned, the team exercising such challenge will forfeit its time-out.
4. If the Coach's Challenge does result in the call on the ice being overturned, the team successfully exercising such challenge will retain its time-out.