He just did not expect it to happen so soon.
After misadventures in Middlesbrough, Turkey and the United States, the Scottish Premier League's all-time top scorer rejoined his first club on Saturday at the age of 29, and Hay feels a spell at Rugby Park could help his old pal rediscover his mojo. Boyd, who conducted the half-time draw on Saturday, has not played since September but may feature in Wednesday night's trip to Easter Road.
"I had spoken to him a wee while ago and was joking with him, saying 'come on back to Killie' but I genuinely didn't know this was happening until Friday night," said Hay. "I maybe thought he would be back here a couple of years later than this, but you never know what is round the corner. The type of player he is he could have a good six or seven years in him. If we can get a good couple of months out of him and help him on his way that would be great."
When he moved to Rangers Boyd donated his signing-on fee to the youth development programme at Rugby Park, and it would be further payback if he can score a few goals to help Kilmarnock up the table.
Having said that, finding a berth in the team could be prove a problem. The club are in decent form, tend to employ a 4-2-3-1 shape, and at first glance Boyd's game is rather similar to in-form Irishman Paul Heffernan. Cillian Sheridan is another attacking asset.
"He [Boyd] thrives on other people creating chances for him," said Hay. "With Boydy, Heff, Cillian, William Gros and young Rory McKenzie we have got a bit of firepower and any three of them could play together, or two. It gives the manager real options."
Heffernan demonstrated those striking instincts just before the break to cancel out Rory Fallon's excellent volleyed opener, but Aberdeen left Ayrshire cursing the shot-stopping prowess of Cammy Bell and referee Euan Norris. Bell had taken too long to clear and succeeded in sending Niall McGinn crashing to the turf inside the box, only for the official to interpret this as simulation and book the Northern Irishman.
Fallon rued the club's ill-luck, and next up for Aberdeen are a resurgent Ross County side tomorrow. "It could have been a drubbing but it wasn't to be," he said. "Even the goalkeeper said it was a penalty but he was playing to the whistle so it is not his fault. Hopefully those two points don't end up costing us."