McDonald wins it for Gills
Arsene Wenger was relieved to see Arsenal return to winning ways on Saturday, as they overcame Aston Villa.
An FA Cup humbling at the hands of Championship side Blackburn Rovers and a UEFA Champions League mauling by Bayern Munich had heightened tensions in and around the Arsenal camp heading into the weekend.
The Gunners were, however, able to collect a third consecutive Premier League success as Santi Cazorla struck twice against Villa to lift the Gunners to within a point of the top four.
"I am relieved, of course, because it was important to get the three points today," Wenger told Sky Sports afterwards.
"We are on a good run in the Premiership. We were affected by our two major disappointments we had, you could see that on the nervous side, but we have a good spirit in this team and they were focused and determined.
"Even when it came back to 1-1, we found the resources to win the game. We could have scored many, many more goals today, but the most important thing was to get the three points.
"In the last 12 games in the Premiership, we lost two - one was against Man City with 10 men from the start and one at Chelsea. We are on a positive run and let's continue that."
Wenger saw Cazorla break the deadlock with just six minutes on the clock, and he concedes that it was important for Arsenal to start positively in front of a disgruntled Emirates support.
He added: "It was very important.
"The fans were great. Our fans are intelligent and know that we are in the battle to get as close as possible to the top and that we need their support.
"No matter how disappointed you are after the Bayern Munich game, what is important is to stick together and get the points and the wins.
"It has been a very demanding week physically and nervously and it was important not to feel sorry for yourself. We responded in a strong way today."
The Spireites started brightly but Gillingham were only denied a goal by a stunning save from Tommy Lee in the 10th minute to turn away a low shot from Chris Whelpdale.
Lee rescued his team again six minutes later when McDonald broke clear on the left but Chesterfield responded when Marc Richards fired just over from the edge of the box.
The Gills had been in control in the first half without breaking through but they scored five minutes after the interval when a Myles Weston corner to the near post was flicked in by the head of McDonald.
Chesterfield brought on Jack Lester and the veteran striker twice went close but, despite seven minutes of stoppage time, Gillingham stood firm to stay top of League Two.