While Glamorgan paceman Simon Jones confirmed his fitness for England's fixture next week, it was Pietersen who caught the eye, hitting 57 as Hampshire finished a rain-hit first day 197 for three from 61 overs.
Hants captain Shane Warne won the toss and chose to bat at the Rose Bowl but his side's progress was hampered by the conditions as Jones finished the day with figures of one for 49, his only victim being the opening batsman Michael Brown.
At Trent Bridge, Geraint Jones' wicketkeeping understudy Niall O'Brien provided the most substantial of three Kent half-centuries to retain a foothold for the visitors against leaders Nottinghamshire.
After Dave Fulton and Matthew Walker had begun to make Stephen Fleming's decision to bowl first look faulty on a blustery first day at Trent Bridge and then Ryan Sidebottom pegged Kent back, it was O'Brien's 64 which ensured his team at least shared the honours on 301 all out by stumps.
On a pitch with a little in it for a pace-oriented home attack prepared to bend its back, Fulton put on an 81-run opening stand with Robert Key - and Walker then kept the likes of Sidebottom at bay long enough to prosper temporarily.
In Division Two, Andrew Flintoff was able to add only five overs to his small amount of bowling this season as rain washed out most of the first day's play in Lancashire's Championship match with Somerset at Taunton.
But the England all-rounder showed enough in those 30 deliveries to suggest he will be ready to cause Bangladesh plenty of problems in next week's first Test.
Flintoff bowled three maidens and conceded just six runs, getting plenty of life out of the pitch as Somerset reached 79 for two after losing the toss. Mike Burns was unbeaten on 45.
Only 25.3 overs were bowled before heavy and continuous rain left umpires Mark Benson and Trevor Jesty with no alternative but to abandon play.
Worcestershire will look to build a lead on day two against Essex after the home side were skittled out for only 220 at Chelmsford.
Captain Ronnie Irani smashed 85 before being caught and bowled by Gareth Batty but none of his team-mates managed a half-century as the Worcestershire bowler took three wickets for 26, while Matt Mason proved dangerous with four for 48.
The visitors squeezed in six overs before the close, on 17 without loss.
Durham must start well in the morning if they are to avoid the follow-on as they finished the day 65 for three in reply to Yorkshire's 254.
Richard Dawson (86) was the only Yorkshire batsman to reach 50 with opener Matthew Wood out for a duck, caught by Michael Lewis off Liam Plunkett.
But Tim Bresnan helped make amends with the ball as he dismissed Mike Hussey (26) and Jonathan Lewis (23), who was caught lbw to finish the day with figures of two for 15.
Paul Collingwood was the third to go, dismissed for seven by Deon Kruis.
In the National Cricket League, Surrey enjoyed a comfortable five-wicket victory over Scotland in Edinburgh, while Warwickshire beat Derbyushire by 52 runs.