The Hammers went 2-0 down before drawing level through midfielders Stewart Downing and Matt Jarvis.
"We've still got a lot to work at," McDonald told West Ham TV on a humid afternoon in Hertfordshire. "We've only just been tickling with a football and haven't done much tactical stuff, so when you go into a game against a team who is a week ahead of you in pre-season, you've just got to stand up and be counted.
"We moved the ball quite well, but not as quick as what we should do, but that will come in time. We only created a couple of chances, but as you play more games, your play becomes a little more refined and sharper, so we're happy with everybody getting through 45 minutes. We scored a couple of goals at the end, which were an added bonus, really.
"The atmosphere was brilliant, there was a really good crowd and the players were at it. A couple of times we held on to the ball a little too long and invited the opposition to come on to us, so we have do better as time goes on and I'm sure we will do."
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