Sussex in charge despite Morgan and Finn
Sussex 452 and 109 for 5 v Middlesex 350
Eoin Morgan scored 58 in his first County Championship appearance of the season for Middlesex but Sussex are 211 runs ahead at 109 for 5 in their second innings and remain in control of the Division Two top-versus-bottom match at Uxbridge.
Morgan's innings was the highlight of Middlesex's 350 all out, but he was bowled just before lunch attempting to pull a quicker ball from off spinner Ollie Rayner that also seemed to scuttle through a little low.
It was a disappointing end to a bright 85-ball knock from 23-year-old Morgan, whose first scoring shot was a lofted on-drive for six off Monty Panesar and who later also hit Rayner down the ground for a second six to go with his six fours.
England's Irishman is expecting to be named on Sunday in the squad for the opening Test against Pakistan at Trent Bridge, which starts next Thursday, but first he might have to play another significant innings for his county if Middlesex are to prevent second division leaders Sussex from gaining victory on the final day.
At the close of day three Sussex were in sight of building a potentially match-winning lead, despite some effective new-ball bowling from Steven Finn and Toby Roland-Jones, who took over the mantle when Iain O'Brien limped off the field with a leg injury.
Finn, indeed, opened the innings with a marathon 16-over spell - four before tea and twelve more afterwards - and was fiery enough throughout to suggest that his fitness for next week's first Test is not in any doubt at all.
Corey Collymore was Sussex's best bowler as they worked their way steadily through the Middlesex batting order following the home side's resumption on 127 for 2.
John Simpson did not add to his overnight 58 before being well held by a diving Rayner at second slip off Collymore, but Morgan and Dawid Malan then put on an attractive stand of 103 until Panesar bowled Malan through an over-ambitious slog-sweep.
Neil Dexter and Gareth Berg held up Sussex for a while, but Berg was bowled by medium-pacer Michael Thornely and then Collymore and Lewis Hatchett cleaned up the innings with the second new ball.
Dexter edged Collymore to second slip, Shaun Udal was caught at the wicket to give impressive left-armer Hatchett his maiden Championship wicket, Roland-Jones had his off stump removed by Collymore and Finn was castled by Hatchett.
That earned Sussex a first-innings lead of 102, but if they thought they would romp away from Middlesex with the bat in the final session then they reckoned without the fine combined effort of Finn and Roland-Jones.
From 36 without loss at tea, Sussex lost four wickets for 29 runs as both Chris Nash and Ed Joyce fell to a pumped-up Finn after Mike Yardy had played on to Roland-Jones, who then sent back Matt Prior cheaply even though the England Test wicketkeeper looked baffled to be given out caught behind the stumps.
Murray Goodwin hit 35, and added a hard-fought 40 for the fifth wicket with Thornely, before being trapped lbw by Middlesex captain Dexter.