Swansea suffered a major blow to their race for promotion after a 2nd defeat to the Gills, in the space of less than 2 months.
With Oldham maintaining their good form, they are now just a point behind us as they sit just outside the playoffs in 7th place.
For the trip to Priestfield, Jackett made just one change to the side that beat Brentford 9 days ago.
Adrian Forbes was given a place in the starting line-up as Jackett was pleased with his contribution when he came on as a sub in the 2-1 win against the Bees.
Roberto Martinez?s run in the side didn?t last long as he found himself back on the subs bench.
Jackett had a strong bench available to him which included Way, Knight, Fallon, Martinez and Williams.
Tate ? Monk ? Lowe ? Ricketts
Britton ? Forbes ? O?Leary ? Robinson
Akinfenwa ? Trundle
SUBS: Way, Knight, Fallon, Martinez,Williams.
Darren Byfield?s 54th minute goal from the penalty spot was enough to give the Gills a major boost in their fight against relegation.
They?ve won just 2 points less than Southend on home soil this season so maybe we under-estimated our opposition this week. Football is certainly a funny, or more annoying game sometimes as last week Bristol City thrashed Gillingham 6-0 at Ashton Gate.
Both teams had chances in the first half to open the scoring and take the lead and Swansea?s missed chances proved costly in the second half.
Jackett brought on Martinez for Britton at the start of the second half but 9 minutes in, and we went a goal down.
Keith Lowe brought down Jarvis and he was punished for a mis-timed tackle that looked like it was just outside the box. That didn?t matter as the referee pointed to the spot. Byfield stepped up and his powerful shot went in off the crossbar.
On the hour mark, the ineffective Lee Trundle made way for Leon Knight and Williams came on for Ricketts.
Gillingham looked to put themselves in the comfort zone while the Swans went in search of an equaliser.
The hosts went close from Black?s free kick but Forbes got his head to the ball and luckily it went harmlessly wide.
We never really pushed hard enough to try and get a valuable point out of the game and despite being only a goal in front, they looked comfortable and there was little doubt that the score would stay the same.
A good run until the end of the season is what we?ve needed if we want to gain promotion but we are simply showing no signs that we can do this.
Cue a very similar post match reaction from Kenny Jackett.