A freak head injury to Middlesex captain Adam Voges overshadowed the first day at the Ageas Bowl, where Michael Carberry scored his first County Championship century since September 2014.
Voges, who had earlier elected to bowl without a toss, was struck on the back of the head by a ball lobbed by substitute fielder Ollie Rayner and missed by wicketkeeper John Simpson, after Carberry had hit one of his 14 boundaries.
The Australian fell straight to the floor before being helped off the pitch by two physios, and was subsequently taken to hospital with suspected concussion. He will not make another appearance in this game.
Batsman Carberry looked in fine fettle from the start, especially cracking full balls straight down the ground, and celebrated reaching his ton from 184 deliveries with a crisp back-foot shot through extra cover.
Carberry saw three teammates come and go during his vigil. Fellow opener Jimmy Adams made five before edging Tim Murtagh to Nick Compton at second slip, while captain James Vince appeared as graceful as ever before he was well caught by Voges, off Toby Roland-Jones, for 25.
Will Smith (24) also clipped Roland-Jones into the slip cordon, before Liam Dawson came to the crease to begin a 100-run partnership with Carberry.
The former England Test opener eventually departed for 107 as James Harris collected his 350th first-class wicket, but Dawson continued to impress, despite an abdominal strain, moving past his 50 in 117 balls.
Adam Wheater held up the other end with a patient 25 from 47 balls, but the new ball did its job as Middlesex took three for 20 in six overs.
All three were lbw, with Murtagh claiming the wicket of Wheater, Ryan McClaren (9) falling to Roland-Jones and James Harris removing Chris Wood for six.
Dawson, though, remained unbeaten on 87 and remains key to Hampshire making a big total.
This post was last modified on 02/05/2016