Rovers’ wait for an opening day win goes on after a late Portsmouth equaliser meant they had to settle for a share of the points on the south coast.
Substitute Yengi’s header cancelled out Luke Thomas’ fine opening goal that saw Rovers a goal ahead at the interval.
The visitors, resplendent in their brand new away shirt embossed with braille, opened their League One account for the season by handing starts to summer signings James Wilson, Jevani Brown, Luke Thomas and goalkeeper Matthew Cox.
Rovers began on the front foot in the pouring rain, with Luke Thomas getting in behind the home defence on more than one occasion.
From one of his crosses in the fourth minute, Marquis had a shot blocked, before firing the rebound over the bar.
They went even closer in the seventh minute when Collins rounded the keeper from a Gordon through ball but the angle proved too tight and the ball ended up in the side-netting.
Finley was booked in the eight minute for a late tackle before, moments later, having a shot deflected behind for another Rovers corner.
Wilson and Connolly combined to prevent a Portsmouth opener in the 11th minute as the home side looked to get themselves going.
Rovers deservedly took the lead in the 23rd minute as great work from Finley and Brown set up Thomas, who planted his shot beyond Norris.
The home side went desperately close to an immediate equaliser but Whyte’s shot flashed wide of Cox’s far post.
Wilson picked up a booking in the 34th minute for bringing down Morrell as Pompey broke away.
Marlon Pack took the free-kick on the edge of the D but it flew over the bar.
Hoole picked up the game’s fifth booking in the 41st minute as he was booked for time-wasting.
Connolly pulled off a Cruyff turn and Thomas almost put Brown in on goal with a raking pass, before the fourth assistant signalled eight minutes of added time.
Bishop kneed wide of the target in the second of those additional minutes.
There was time for a yellow card for Towler as he crudely blocked Thomas from making a run.
As the half drew to a close, Aaron Collins almost scored a brilliant goal, spinning on the edge of the area and curling a right-footed shot inches wide.
However, the visitors had to settle for a one-goal lead at the break.
The home side flew out of the blocks as the game resumed, with Whyte forcing a fabulous save from Cox in the Rovers’ goal, before the on-loan ‘keeper was again called into action as he got right behind Bishop’s header.
Connolly was next to excel at the back as the hosts turned up the heat as they won their ninth corner of the game.
Finley won a free-kick after 54 minutes to allow the Gas some respite, but his delivery had too much on it and drifted harmlessly behind.
Collins was unselfish in the 60th minute, teeing up Marquis, whose shot was parried behind for a corner. During the break in play, Connolly made way for the returning Connor Taylor, who joined from Stoke on a three-year deal on Thursday.
Poole was booked in the 63rd minute before Grant replaced Gordon at left-back in Rovers’ second switch of the afternoon.
Rovers had a penalty shout after 72 minutes when Marquis robbed Pack of possession and the Portsmouth man looked like he impeded the Gas striker; referee Allison didn’t agree.
There was a clash of heads in the 73rd minute between centre-backs Taylor and Wilson, which saw the latter come off the worst and requiring treatment.
On the restart, Rovers broke and Thomas’ persistence allowed Collins to get away a low shot on target that Norris got down to claim.
A heavy touch from Taylor went unpunished, much to the home side’s anger, before he atoned a minute later, clearing well when under pressure.
Rovers made a double substitution in the 81st minute, with Sinclair and Evans replacing Thomas and Collins.
Portsmouth almost snatched an equaliser a minute later as Ogilvie’s low long-range effort cannoned off Cox’s left-hand post.
The home side were then appealing for a penalty but settled for a corner, which Rafferty sent too long.
Ward showed excellent skill in the 88th minute, before Brown almost provided a wonderful assist following a crunching Antony Evans tackle.
There would six additional minutes again and, in the first of those, Portsmouth found an equaliser as sub Yengi headed home.
Sinclair tried to catch Norris off his line but the goalkeeper claimed, before Grant was forced to clear for a corner as Portsmouth raced up the other end.
Rovers held on for a point as their 48-year search for a win at Fratton Park continues.
PORTSMOUTH: Norris, Rafferty, Poole, Towler, Ogilvie, Morrell, Pack, Lowery, Whyte, Bishop, Scully.
Subs: Schofield, Raggett, Sparkes, Devlin, Kamara, Saydee, Yengi.
ROVERS: Cox, Hoole, Connolly (Taylor 60), Wilson, Thomas (Sinclair 81), Gordon (64), Ward, Finley (c), Marquis, Brown, Collins (Evans 81).
Subs: Belshaw, Taylor, Grant, Sinclair, Crama, Evans, Jones.
Referee: Sam Allison
Attendance: 19,165 (1,991 Rovers)