The 26-year-old made the step up look easy - accurate in the tight, and showing good speed in a first-half break - with his replacement, fellow new-boy David McGregor, looking equally as comfortable.
Defensively the Exiles - last in the Aviva Premiership in points conceded - held Worcester to just three points until the 53rd minute in what was a relatively open game - before allowing the visitors to cross three times, however two tries coming after Smith rolled his bench.
"We've just to thank John Wells and Dean Richards at Falcons," said Smith. "We put in a mercy call this week and in the space of 15 minutes the came back to us and said no problem, we can lend you Mikey.
"And we've found a young fella named Davey McGregor who Ian Humphreys and James Sandford knew from the Ulster academy and we took him on the strength of their recommendation.
"With four hookers injured, to pick up two guys who played so well, having trained with us for just one day - I'm delighted.
"Defensively we were very good in the first half - we got off the line well, we hustled. We didn't drop off.
"With the changes in the second half things got a bit ropey, and I wasn't happy with the urgency in defence but it was a good result."
Worcester's season has taken a different course, while Irish are still desperately seeking momentum needed to turn around their Aviva Premiership season, Richard Hill was able to use the game to test some of his young players and give some of his more established names, and older bodies, some rest time.
Coming off the back of an Amlin Challenge Cup double-header where they averaged over 75 points, Worcester director of rugby Hill acknowledged his side were never going to be at their sharpest on defensive end.
However, with the return of defensive guru Phil Larder to the Warriors camp this week, Hill insists his side are well-placed to refocus and retool ahead of their Aviva Premiership run-in.
"They [London Irish] went full bore," said Hill. "They put their full side out - we've kept a lot of players back."
"We knew when we saw their team announced that, away from home, it was going to be a tough ask.
"But I was pleased with our penalty count, I was pleased with our scrum and line out and we scored three tries away from home.
"It's a bizarre one for me to look at because so many of the areas of the game were so good but we leaked the tries so easily.
"I can forgive them because we've had two weeks in the Amlin Cup where we haven't had to do any defending and we've done no defence in the last three weeks.
"Next week Phil Larder comes back in. He's not been in for three weeks and this is probably a fitting game for him to analyse and get us back on the straight and narrow.
"If we can bolt on our defence - which is normally pretty strong - next week should be a different story."
London Irish: Homer, Ojo (Watson 62), Armitage, Tagicakibau, Yarde; Geraghty (Humphreys 67), Phibbs (Moates 62); Lahiff (Yanuyanutawa 63), Mayhew (McGregor 63), Aulika (Halavatau 63), Skivington (Sandford 63), Evans, Garvey (Low 56), Sinclair, Gray
Worcester Warriors: Classens (Goode 52), Drauniniu, Clarke, Matavesi (Short 52), Lemi; Gray, Arr (Frost 62); Jones (Andress 62), Hayes (Shervington 62), Currie (O'Donnell 62), Schofield, Gillies (Percival 62), De Carpentier, Abbott (Betty 62), Cowan
Scorers
London Irish
Tries: Yarde 3, Aulika 2, Gray
Conversions: Homer 5
Penalties: Homer 2
Worcester Warriors
Tries: Gray, Lemi, Percival
Conversions: Gray, Goode 2
Penalties: Gray
Attendance: 5,038
Referee: Leighton Hodges
