An 86th-minute goal from Christophe Berra settled a disappointing affair in which Scotland were frustrated for long periods by the goalkeeping of Northern Ireland's Michael McGovern.
Next for Scotland is a crucial Euro 2016 qualifier with Gibraltar on Sunday.
Strachan told Sky Sports: [The] start was good, a lot of efforts on goal. We broke through a lot early in the game. Alright at the start of the second half, goalkeeper has made some good saves. Then it died again, then the last 15 minutes we came on again.
"I'm happy a lot of lads who have not played a lot recently got a game. I thought our shape was good, there are one or two things I'd like to work on, but we'll do that."
Despite being on the back foot for most of the encounter, Northern Ireland boss Michael O'Neill believes his team can take plenty of positives from the game.
O'Neill said: "We can take an awful lot [from the performance], we ended up with three [players] under 20 [years of age] on the pitch, so it is great for those lads to get minutes in that type of game.
"I was really pleased with [midfielder] Stuart Dallas, I thought he did very well. It was good to see [captain] Jonny [Evans] back, I thought he was excellent throughout the 80 minutes he was on.
"We allowed Scotland to press us at times, and maybe didn't create as much as what we would have liked, but there were more positives from the performance than negatives."
